Reeenable tryLocalExecution() test in ClientTest
Change TypeExtractor to have non-static methods that do the actual work

This is required because we need state to detect recursive data types.
This will become necessary when introducing Pojo Types.
Add support for POJO objects

This adds support in the TypeExtractor and also one can now use field
expressions for grouping, join, and co-group.
Removed redundant config constants value.
Fix buggy computation of TaskManager free memory size

- In NepheleMiniCluster the memory size was divided twice by the number of TaskManagers
- In HardwareDescriptionFactory the memory fraction config value was multiplied too early
Fix the managed memory planning after patch 9ce6293075d1a2326df8a2e99c032445a555b28b
Fix checkstyle errors and various warnings.
Add "How to contribute" and "coding guidelines" to the project.

[ci skip]
Add first files for system internals documentation

[ci skip]
Add various figures for internals.
Update text on internals overview.

[ci skip]
Fix simple error in local execution memory estimation
Add "how to add an operator" section to internals.
Add stubs for other internals pages

[ci skip]
Mention that Oracle JDK 6 library will fail to build

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
Minor changes in Java POJO WordCount example
add gh_link jekyll plugin to docs
Finished Flink-928

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
[FLINK-888] Add swap() to Tuple2
[FLINK-893] Inconsistent Iteration Step Function gives nonesense error message

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
[FLINK-932] Introduce automatic generation of semantic props for projections

This closes #29
Fix various error messages and invalid JavaDocs.