Reworked, cleaned up and fixed some splitter problems (not manifested in Spark's case)

1) #draggable still wrong when splitter size > 1
2) splitter position doesn't get restored on startup
Fix: splitter's #draggable was not set correctly for splitter's size > 1
Add attributes for min/max target size to spark-splitter & spark-split-view
Force initial target size to be within specified min/maxTargetSize
Fix: saved splitter position was read correctly but not propagated to splitter
Undo inadvertent change
Merge pull request #1962 from ussuri/fix-spark-splitter

Fix spark-splitter