Remove debug LOG message of TaskManager heartbeats
[FLINK-985] Update the config.md to properly describe the configuration settings.

[ci skip]
Fixed Bug Flink-978

https://issues.apache.org/jira/browse/FLINK-978

Author: Jonathan <Jonathan@Hasenburg.de>

Closes #46 from JonathanH5/fixWebI and squashes the following commits:

13a7d41 [Jonathan] Fixed Bug Flink-978
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
Add "How to contribute" and "coding guidelines" to the project.

[ci skip]
Fix the managed memory planning after patch 9ce6293075d1a2326df8a2e99c032445a555b28b