Add new pmlog context for 3rd party app developers

:Release Notes:
Add new pmlog context and file redirection for 3rd party
app developers

:Detailed Notes:
This new context will be added in default.conf. This context will direct
logs to both /var/log/messages and /media/developer/log/dev.log.
Duplication is to make sure we show only logs from this context to 3rd party
app developers, and also upload them to the server (along with other logs).

:Testing Performed:
Compiled and tested that the change routes logs from context
to both /var/log/messages and /media/developer/devlog.

:QA Notes:

:Issues Addressed:
[ANG-845] SDL needs PmLog context for 3rd party app developer

Open-webOS-DCO-1.0-Signed-off-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>

Change-Id: I9eeab8feadc972f80849d38a3104ff0fc10a0b93
Reviewed-on: https://g2g.palm.com/4530
Reviewed-by: DCO Verification
Tested-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>
Reviewed-by: Dongsun Kim <dongsun.kim@lge.com>
Reviewed-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>