Update angular-translate.d.ts

Add definitions for https://github.com/angular-translate/angular-translate/blob/master/src/service/loader-partial.js
Update angular-translate.d.ts

Fix Bug. registerAvailableLanguageKeys accepts ILanguageKeyAlias object hash, not array of ILanguageKeyAlias
Rename ITranslatePartialLoader into ITranslatePartialLoaderService
Rename addPart and deletePart return value
Merge pull request #2434 from Saftpresse99/master

Update angular-translate.d.ts