GPII-209: removed grades for request handlers
GPII-209: removed demands merging code from config loader.
GPII-209: Removed all demands except for get and set for data source.
GPII-209: removed writable check in pre init function.
GPII-209: updated data source grades and tests.
GPII-209: removed all demands from kettle.
GPII-209: renamed getWritable dynamic grade into getWritableGrade.
GPII-209: removed abmiguity with the callbackWrapper name.
GPII-209: added handler check for server onHandlers event.
Merge branch 'GPII-209'

* GPII-209:
  GPII-209: added handler check for server onHandlers event.
  GPII-209: removed abmiguity with the callbackWrapper name.
  GPII-209: renamed getWritable dynamic grade into getWritableGrade.
  GPII-209: removed all demands from kettle.
  GPII-209: updated data source grades and tests.
  GPII-209: removed writable check in pre init function.
  GPII-209: Removed all demands except for get and set for data source.
  GPII-209: removed demands merging code from config loader.
  GPII-209: removed grades for request handlers