Add volume test

:Release Notes:
Test gives info about dependency between the size of the database and the performance of DB operations.

:Detailed Notes:
- get available space on the disk via DB8 request 'spaceCheck';
- create 10 iterations (number is configurable);
- put data to DB8 with volume = 1/10 of available space (using 'put' operations);
- run performance test and save 4 time values;
- continue iterations till 10;
- show report on the screen.

:Testing Performed:
tested on local build

:QA Notes:

:Issues Addressed:
[BHV-6877] [DB8] Volume testing

Open-webOS-DCO-1.0-Signed-off-by: Igor Kuksyuk <igor.kuksiuk@lge.com>

Change-Id: I5fcd59cc7250f4179d2e30f4585ebb6621a0ed2a
Reviewed-on: https://g2g.palm.com/5568
Reviewed-by: DCO Verification
Tested-by: Igor Kuksyuk <igor.kuksiuk@lge.com>
Reviewed-by: Maksym Sditanov <maxim.sditanov@lge.com>
Reviewed-by: Igor Kuksyuk <igor.kuksiuk@lge.com>