This now covers both Java and Scala.

The switch to kramdown is necessary because I want to add tabs in the
documentation for code examples and Redcarpet does not allow markup
inside divs.

Before, some doc pages had "#" headings as toplevel headings while
others had "##" (which is the same as --- underlined headings). Now we
user level 2 everywhere. The page title is still a h1 heading.

This better reflects what it is actually for. It is still derived
from TupleTypeInfoBase, though.

Also actually use termination criterion in TransitivelClosureNaive
Java example.

Add ConnectedComponentsITCase for Scala Example

Also fix some formatting in the example code

Add WebLogAnalysisITCase for Scala Example

Some minor reformatting of example code and scaladoc.

Add ITCases for TriangleEnumeration Scala Examples

Also fix some formatting and make TriangleEnumerationOpt Scala produce the
same output as the Java version.

Add PageRankITCase for Scala Example

Also fix formatting in PageRank Scala Example.

Fix formatting in EnumTriangles Scala Examples

Remove Old/Deprecated Scala Examples and ITCases

Fix formatting in EnumTrianglesBasic.scala

Fix formatting in LinearRegression Scala Example

Remove old Scala LineRank Code and RelQuery Example

[scala] Fix typo in scaladoc in GroupedDataSet

[scala] Fix Scaladoc of Join and CoGroup Operation

Was still referring to the type of join/coGroup function that returns an
Option.

Fix tab vs. spaces in flink-scala and flink-scala-examples

Some occurences in comments and POMs where not updated.

Also change signature of join and coGroup to always return a value, not
an Option.

This is very naive right now, just checks whether a function of the same
name is available. There are lists and regex patterns of excluded
functions since not all functions in the Java API need to be available
in the Scala API.

Fix join operator to user proper EquiJoin constructor so that semantic
properties are actually retrieved.

Fix typo, getSematicProperties -> getSemanticProperties

This does not change the runtime behavious. The key field names are
mapped to tuple indices at pre-flight time.

Also extends tests to cover the new feature.

Don't bother looking at the diff, this is almost a complete rewrite of
the previous Scala API. This uses all the work put into the Java API,
such as TypeInformation, the serializers and comparators and the
operators.

The Scala DataSet and ExecutionEnvironment wrap their respective Java
equivalents. TypeInformation is generated by a macro that uses
TypeInformationGen and other macro support classes. The Java
TypeExtractor is completely bypassed but the TypeInformation and
sub-classes are created by the Scala type analyzer. There is special
support for Scala Tuples in the form of ScalaTupleTypeInfo,
ScalaTupleSerializer, and ScalaTupleComparator.

This also adds tests to flink-scala that are ports of the tests in
flink-java.

There are not yet any Scala specific tests in flink-tests. All the
scala example ITCases are commented out, as well as the examples
themselves. Those will be uncommented once the examples are ported. This
will happen in separate commits.

They were in api.java before but they can be used from Scala,
just like the regular functions.

Previously both sides were always wrapped/unwrapped, even if one side
was a tuple type. This was not compatible with the Scala tuples and is
also not necessary anymore because of the GenericPairComparator.

This is necessary because the previous test didn't work for Scala tuples.

Was TupleComparator before which does not work when used from the Scala API.

I'm doing this in preparation for the Scala API rework, since then I can just copy over
the operators package and use them for Scala.

Before, FlatMapOperator, GroupReduceOperator, MapOperator, and MapPartitionOperator
performed the Type extraction themselves while the other Operators had TypeInformation
parameters. Now the are all unified, which makes it possible to use them from the
Scala API.

Also Key extraction for selector functions is moved outside of Keys.java

Now we have TupleTypeInfoBase, TupleSerializerBase, and TupleComparatorBase. They
are now super classes of TupleTypeInfo and the others.

Also rename compare on DataInputView to compareSerialized because Scala
cannot distinguish between the to compare methods for some reason.

This change is necessary for allowing the Scala API to reuse most of the
functionality.

The GenericPairComparator uses the new extractKeys method of
TypeComparator to compare values of any type. This replaces
TuplePairComparator and some other special-case pair comparators. This
is preparatory work for enabling support for Scala Tuples and POJO
comparators.

This closes #94

This closes #117
* each key is associated with the number of times it was inserted into the accumulator
* backed histogram with a tree map to present the entries sorted by key

This closes #120

This closes #124

Temporarily disabled streaming tests that validate jobgraphs that used to be illegal, but are now legal.

Small fix in integration test

Tolerate concurrent scheduling attempts

Make Co-Location constraints resilient aginst out of order scheduling and depply integrate them with slot sharing
Fix miscellaneous checkstyle errors/warnings