[FLINK-1239] [streaming] IterateExample fix and parallelism setting in StreamExecutionEnvironment made public

Conflicts:
	flink-addons/flink-streaming/flink-streaming-examples/src/main/java/org/apache/flink/streaming/examples/iteration/IterateExample.java
[FLINK-1233] Fix flaky AggregateITCase
[docs] Add description of Quasiquotes compiler plugin in Eclipse to FAQ
[FLINK-1242] Fix streaming-examples and scala-examples POMs to work properly with Eclipse
[FLINK-1008] Fix createProgramPlan() throws exception

Problem was, that ExecutionEnvironment#getExecutionPlan clears the data
sinks, i.e. a following ExecutionEnvironment#execute will throw an error
because there are no data sinks.

This introduces a new flag for ExecutionEnvironment#createProgramPlan to
indicate, that the the sinks shall not be cleared.
This does not break any existing code.

This closes #184
[FLINK-890] [docs] Adjust examples to show reader methods and correct class-vs.-interface errors.
[FLINK-1244] setCombinable() returns operator

This closes #205
[FLINK-1172] [docs] Fix broken links in documentation

This closes #206
Fix flaky test SumMinMaxITCase
deprecated current aggregation code
Test cases and API for new aggregations
ungrouped aggregations
grouped aggregations