[storm-compat] Moved Storm-compatibility to flink-contrib and split flink-contrib into small sub-projects

Closes #573

  - re-introduced possibility to specify output type for addSource()
  - split StormCollector into Abstract-, Bolt-, and Spout-Collector
additional minor changes:
  - removed unnecessary "unused" tags
  - fixed comment typos
  - added missing license header in SingleJoin example files

This closes #831

This closes #829

This closes #826

This closes #827.

- Removed unused constructor parameter.
- Updated outdated and wrong connection javadocs.

Closes #825

Closes #820

Also adding a log message when delaying the retry of the execution graph.

Closes #819

This closes #824.

- we already decided to host them on the website
- not really useful and they need maintenance
- having the snapshot quickstart in the source is against Apache rules

This closes #822.

This closes #821

This closes #792.

Closes #816

The closure cleaner still cannot be disabled for the Timestamp extractor
in Time and for the delta function in Delta (windowing helpers).

Closes #813

This closes #817

- The description of the input format for the graph examples
  showed an example input as having a newline at the end
  of the last line, but CsvInputFormat doesn't allow that
  (it says "Row too short" for the empty line).
- Fixed a link to local_execution.html in a javadoc.
- ConcatenatedExtract had a typo in its name.
- The creation of the jar for the SessionWindowing example was missing
  from the pom.

Closes #809

[FLINK-2194] [type extractor] Excludes Writable type from WritableTypeInformation to be treated as an interface

This closes #814.

Closes #810

Closes #804

When comparing the hostname, it was comparing capitalised vs.
all-lowercase hostname from the yarn config.

[ml] Makes StandardScalers state package private and reduce redundant code. Adjusts flink-ml readme.

[FLINK-1844] [ml] Add MinMaxScaler implementation in the proprocessing package, test for the for the corresponding functionality and documentation.

This closes #798.

This closes #796.

Closes #806