Add Open Callsite action in events table for CTF events

Add Open Callsite action in events table for CTF events

- Create CtfTmfCallsite class
- Add interface to CtfTmfEvent to get callsite for an event
- Remove callsite from CtfTmfEvent content fields
- Add Open Callsite action to TmfEventsTable
- Fix search for callsite candidates in workspace
- Add dialog when more than one candidate are found
- Change action name for callsite and model to be consistent
- Fix capitalization of actions in events table
- Make CtfTmfEventFactory a final class with no public constructor
- Rename CtfCustomAttributes to CtfConstants and add context strings

Change-Id: I82523209ef960d37f7f0efa40684e7a92a593ebe
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/8374
Tested-by: Hudson CI