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.
[FLINK-996] Fix for bug in union replacement

This closes #56
[FLINK-990] Added constant fields and combinable annotations forwarding to Scala API

This closes #51
[documentation] modified gh_link to support naming
[documentation] fix internals linking
[documentation] fixed a lot of links, better gh_link plugin

This closes #54
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
[FLINK-994] Replaced DataInput and DataOutput with DataInputView and DataOutputView
[FLINK-994] Added test cases for AbstractPagedInputView, fixed problem with hbase.

This closes #53
[FLINK-836] Integration of the CachedBuildSideMatchDriver into the optimizer
[FLINK-795] Tests for the integration of the cached match driver into the optimizer
[FLINK-836] Rework of the cached match driver
Fix various JavaDoc errors
Clean up exception logging in JobManagerITCase.
[FLINK-701] Rework of TypeExtractor for SAM support

This closes #52