ConfigKEys.getStaticKeysOnClass: improve logging

- if get exception for a field, then log which field was causing the
  problem
Deletes keys defined in ConfigKeys

- Update all uses to the new BrooklynConfigKeys
- Was previously deprecated, with fields in ConfigKeys referencing
  those in BrooklynConfigKeys. But this led to strange NPEs where
  ConfigKeys fields were null (presumably due to ordering of
  initialising the two classes' fields)!
- Breaks backwards compatibility, but better to have a compilation error
  than a weird NPE.
Merge pull request #930 from aledsage/fix/NPE-from-ConfigKeys-fields-strike2

Fix: NPE from ConfigKeys fields
Changes to brooklyn core to store Application and Location creation and deletion events
Location usage tracking: aled's changes
Refining ApplicationUsage structures
Adding useful metadata to JcloudsSshMachineLocation.toMetadataRecord()
Adding ApplicationUsage and MachineUsage calls to rest api