CDAP-538: Ported procedures of Purchase app to services.
Merge branch 'develop' into CDAP-538-purchase-app

Conflicts:
	cdap-examples/Purchase/src/main/java/co/cask/cdap/examples/purchase/PurchaseApp.java
CDAP-538: Fixed build after merge with develop.
CDAP-538: Updated docs and scripts.
CDAP-538: Reverted body retrieving as it's in develop.
CDAP-538: Removed unused import.
CDAP-538: Removed unnecessary method from service; Added test for PurchaseHistoryService; Moved handler into the PurchaseHistoryService class.
Merge remote-tracking branch 'upstream/develop' into CDAP-538-purchase-app
Merge remote-tracking branch 'upstream/develop' into CDAP-538-purchase-app
CDAP-538: Updated response when history not found; Updated tests to waiting service startup.
CDAP-538: Updated docs of PurchaseHistoryService.
CDAP-538: Updated order of services in the scripts.
CDAP-538: Removed TODO; Replaced service startup check to private method.
Merge remote-tracking branch 'upstream/develop' into CDAP-538-purchase-app
CDAP-538: Used method from TestFrameworkTest to wait service startup.
Merge pull request #621 from cybervisiontech/CDAP-538-purchase-app

CDAP-538: Ported procedures of the Purchase app to services.