Provide mechanism to track DB usage on-device

:Release Notes:
Db8 notify when usage has crossed threshold (85.0, 90.0, 95.0)
Alert event when DB usage hits critical levels (95%)

:Detailed Notes:
Add space check for mediadb and tempdb
Move Space Alert functionality into MojDb

:Testing Performed:
Compiled and tested localy.

:QA Notes:

:Issues Addressed:
[GF-53321] Provide mechanism to track DB usage on-device

Open-webOS-DCO-1.0-Signed-off-by: Maksym Sditanov <maxim.sditanov@lge.com>

Change-Id: I33da94c396fb572505d81343b03f00f50d05c4e7
Reviewed-on: https://g2g.palm.com/4212
Reviewed-by: DCO Verification
Tested-by: Maksym Sditanov <maxim.sditanov@lge.com>
Reviewed-by: Igor Kuksyuk <igor.kuksiuk@lge.com>
Reviewed-by: Maksym Sditanov <maxim.sditanov@lge.com>