Implement call task framework

:Release Notes:
Implement call task classes with support for synchronous and
asynchronous replies receiving

:Detailed Notes:
Add LSGMainGetContext function for main loop context retrieving
Add Call wrapper class for LSCallXXX function family and call
life-time management
LS::Service extended for providing LS::Call
Add helper services support to run_with_hub script

:Testing Performed:
Unit/integration tests on desktop build

:QA Notes:

:Issues Addressed:
[BHV-1541] Implement call task framework

Open-webOS-DCO-1.0-Signed-off-by: Oleksii Rudenko <oleksii.rudenko@lge.com>

Change-Id: I2d53a40d8fb5ff9a992a3c533eefc3d48095b698
Reviewed-on: https://g2g.palm.com/5312
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>