[FLINK-1363] [runtime tests] Fix race condition in ExecutionVertexCancelTest.testSendCancelAndReceiveFail

This closes #288

[FLINK-1259] [apis] Added comments to interface and docs that filters must not mutate date elements.

This closes #267

This closes #278

 - Remove obsolete code from old IPC net utils
 - Smaller Writable/IOReadableWritable serialzation buffer start size (most messages are rather small)
 - For message logging, make system calls (timestamps) only in debug mode
 - Clean up warnings / code simplifications

Simple code cleanup to remove full package name for FlatMapOperatorBase for FlatMapOperator#translateToDataFlow method

Author: Henry Saputra <hsaputra@apache.org>

Closes #272 from hsaputra/remove_packagepath_flatmapoperatorbase and squashes the following commits:

8ce5abd [Henry Saputra] Remove full package name for FlatMapOperatorBase for FlatMapOperator#translateToDataFlow method.

[FLINK-1335] [docs] Update internals with brief description about JobManager data structures and scheduling.

This closes #281

This closes #280

This closes #275

[streaming] Updated connector type handling to suport generic classes by GenericSourceFunction interface

[scala] [streaming] Changed return types to implicits

[scala] [streaming] added initial ConnectedDataStream support (no windowing,batching) for the scala api

[scala] [streaming] updated example with scala delta helper usage