Added platform to uniqueID

Examples:
Ubuntu: uniqueId="Ubuntu_12.04-64bit-zlib1g-1:1.2.3.4.dfsg-3ubuntu4"
Fedora: uniqueId="fedora_19-32bit-zlib-devel.i686-1.2.7-10.fc19"
Changed test to check architecture in uniqueID
Changed test to check architecture in uniqueID
Merge branch 'issue64-arch-in-uniqueid' of https://github.com/tnc-ba/swidGenerator into issue64-arch-in-uniqueid

Conflicts:
	tests/test_SwidGenerator.py
Extracted get_os_string to common base class
Merge pull request #6 from tnc-ba/issue64-arch-in-uniqueid

Added platform to uniqueID