Bug 1088007 - Ehance utils.getProperty to accept multiple properties files. r=aeftimie, r=amatei, r=hskupin

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branch : mozilla-beta
extra : transplant_source : %F8%19%3E%C2%13%81%5C%BC%1B%1A%20%B4%0B%27A%D9%0CS%CFL