webos.inc: Show branch, revision and description of TOPDIR

:Release Notes:
Include 3 new variables in build header and build-id.txt.

:Detailed Notes:

:Testing Performed:
Only build tested.

:QA Notes:
No change to image.

:Issues Addressed:
[ES-1014] Record commit id of build-* repo in build-id.txt (or
          elsewhere)

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>

Change-Id: Ic0b0fd45afce792d7f911c495cb79d3c4a4e1c68
Reviewed-on: https://g2g.palm.com/6036
Reviewed-by: DCO Verification
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Build: Susan Montooth <susan.montooth@lge.com>
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>