Bug 915884 - Add tests for Inter-App Communication API (part 1, create InterAppCommService.jsm). r=ferjm

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rename : dom/apps/src/InterAppCommService.js => dom/apps/src/InterAppCommService.jsm
Bug 915884 - Add tests for Inter-App Communication API (part 2, xpcshell tests for InterAppCommService.jsm). r=ferjm
Bug 915884 - Add tests for Inter-App Communication API (part 3, clean up the alignment). r=ferjm