fix(injector): allow multiple loading of function modules

move the loadedModules lookup to be performed only on strings in order to allow loading functions that look the same. this issue caused only the first `angular.mock.module(object)` invocation to work since the loadModules lookup blocked all following invocations.

closes #7254
initUid is the same as the old approach of returning ['0', '0', '0'] --- yes it could be minified a bit smaller but I dunno. ask igor about that.