[FLINK-1327] [core] Fix wrapping of MemorySegments in ByteBuffers
[streaming] Basic support reading from local and distributed file systems in readTextFile methods

Conflicts:
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/JobGraphBuilder.java
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/environment/StreamExecutionEnvironment.java
[streaming] ReadTextFile re-implemented as RichFunction and cleanup

Conflicts:
	flink-addons/flink-streaming/flink-streaming-core/src/main/java/org/apache/flink/streaming/api/environment/StreamExecutionEnvironment.java