[FLINK-944] Consolidated serialization logic between different classes. Fixes for warnings.
Rework the Taskmanager to a slot based model and remove legacy cloud code

Squashed commit of the following:

  - Post merge cleanup
  - Renamed fractionMemory into memoryFraction.
  - Removed Local and QueueScheduler and replaced it instead with an unified DefaultScheduler.
  - Removed Local and ClusterManager and inserted instead an unified DefaultInstanceManager.
  - Removed connection IDs from execution edges
  - Removed InstanceType, InstanceRequestMap, InstanceTypeDescription, InstanceTypeDescriptionTypeFactory, PendingRequestsMap
  - Fixed problems with test cases.
  - introduced simple slot system for scheduling.
  - Removed subtasks per instance
  - Added registerTaskManager to the JobManager RPC calls. RegisterTaskManager is called only once where the hardware description information is sent.

Add: Merging cloudmodel remove with new network stack