Add tests for explicit cache removal when hash table is cached

Fix estimation bug in channels
Add tests for isolated cost formulas
Add tests for channel class in plan candidates

Fix various JavaDoc errors.

This closes #52

This closes #53

First cleanup attempt, mostly on Scala code, to follow guidelines from http://docs.scala-lang.org/style:
1. Remove return statement from Scala code where it is not necessary (end of method definition)
2. Remove extra ; from Scala and Java code
3. First drop to abide to 100 chars per line for Scala code.
   Will send another PR for other files as I have encountered.
4. Remove parentheses for empty argument methods that do not have side effect
   (see http://www.artima.com/pins1ed/composition-and-inheritance.html#i1343251059-1)
5. Remove unused import statements in Scala code as I have encountered them.

This is first drop to refactor and clean up Scala code to see comment/ response from community.
More PRs for follow up code will come.

Close #64

This closes #54

This closes #51

This closes #56

This closes #29

I adjusted the error message.

Author: Markus Holzemer <markus.holzemer@gmx.de>

Closes #50 from markus-h/iteration_translation_exception and squashes the following commits:

34a6f87 [Markus Holzemer] adjusted error message when encountering a translation failure for iterations

Taskmanagers are now displayed in the web interface @rmetzger

Author: Jonathan <Jonathan@Hasenburg.de>

Closes #43 from JonathanH5/webclient and squashes the following commits:

5cc5f72 [Jonathan] Finished Flink-928 and simplified how new pages to the WebInterface are added

So people won't encounter and ask the same question as I did just now ;)

Author: Raymond Liu <raymond.liu@intel.com>

Closes #49 from colorant/doc and squashes the following commits:

90bf2aa [Raymond Liu] Mention that Oracle JDK 6 library will fail to build

Add stubs for other internals pages

[ci skip]