Sync up pmlog behavior on engineering and production builds

:Release Notes:
To sync up pmlog behavior between engineering and official builds,
this change introduces a config option in default.conf to enable
'context logging' - that is parse context configs when option is
enabled. By default, this option will be set to false.

:Detailed Notes:
Currently, pmlog behaviour is different on engineering builds and
production builds. The behaviour is also different between nfs and flash
(official) builds. pmloglib/daemon creates multiple context log files in
/var/log/ or non-official or nfs builds. Whereas it creates just one
running log file for official and production builds. The default logging
levels of contexts also differ.

This makes testing and development workflow difficult for those working
with custom/local build for boot time and performance related work.
This also sends limited logs for analytics to the QA cloud server
To make sure we send the same analytics logs to both QA and production cloud
server, there should be no difference between developer and official builds.

To resolve this, we introduce a config option in default.conf to enable
'context logging' - that is parse context configs when option is enabled.
By default, this option will be set to false.

:Testing Performed:
Tested that /var/log/ has multiple context log files when
contextLogging option is set to true. By default (when option is false),
only messages and legacy-log log files are generated in /var/log/

:QA Notes:

:Issues Addressed:
[ANG-272] Sync up pmlog behavior on engineering builds and production builds

Open-webOS-DCO-1.0-Signed-off-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>
Change-Id: Ifcd430b33d4382e00211f18e39cb1e0c11cbe157
Reviewed-on: https://g2g.palm.com/4420
Reviewed-by: DCO Verification
Reviewed-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>
Tested-by: Gayathri Srinivasan <gayathri.srinivasan@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>