Make the packaging script consistent with PMC's

- version number defauls to $(git describe --tag)
- fix a bug in which $pkgver wasn't expanded as quoted with '

Change-Id: Ie7d396045337aaec49d36664f05dbc73a4fb50bd
Support RHEL7 in RPM pacakge

- installs the code to library path both for python 2.6 and 2.7

Implements: MN-2970

Change-Id: Iecf2a8d0b485919e387ad80781e688c71c0337c0
Merge topic 'rhel7'

* changes:
  Support RHEL7 in RPM pacakge
  Make the packaging script consistent with PMC's