[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
[FLINK-1246] Add additional debug output to flaky recovery test
[tests] Various stability fixes to tests
[build] Manage version of joda-time to prevent conflicts between dependencies.
[FLINK-1207] Context environments are realized through factories
  - local execution blocking is reset after each run
[FLINK-1237] Add support for custom partitioners
  - Functions: GroupReduce, Reduce, Aggregate on UnsortedGrouping, SortedGrouping,
               Join (Java API & Scala API)
  - Manual partition on DataSet (Java API & Scala API)
  - Distinct operations provide semantic properties for preservation of distinctified fields
  - Tests for pushown (or not pushdown) of custom partitionings and forced rebalancing
  - Tests for GlobalProperties matching of partitionings
  - Caching of generated requested data properties for unary operators

This closes #207
[bin] Remove MaxPermSize parameter for JVM 1.8

This closes #200.
[FLINK-1209] [compiler] Improve error messages when forgetting to close an iteration
[FLINK-1250] [config] [docs] Correct and document config keys for heartbeat intervals and timeouts

This closes #212
[FLINK-1247] [docs] Fix broken links in documentation

This closes #213.
Minor code clean up to get rid of IntelliJ IDEA warnings

This closes #214.
Add byte array serialization to InstantiationUtil
Added getExecutionEnvironment to the DataSet of the Scala API.
[FLINK-1254] [compiler] Fix compiler bug for pipeline breaker placement

This closes #216
[FLINK-1253] [tests] Make sure tests do not die with garbage collection overhead exceeded

This closes #217
[FLINK-933] Add primitive input format to read a sequence of primitives

This closes #47