Bug 940884 - 1/3: B2G SMS: Create MobileMessageDB.jsm for automation tests. r=khuey

--HG--
rename : dom/mobilemessage/src/gonk/MobileMessageDatabaseService.js => dom/mobilemessage/src/gonk/MobileMessageDB.jsm
Bug 940884 - 2.a/3.  Changes to adopt MobileMessageDB.jsm. r=gene
Bug 940884 - 2.b/3. Move init functions out of MobileMessage constructor. r=gene
Bug 940884 - 3/3. test cases. r=gene