test($translatePartialLoader): initial tests

Initial tests for $translatePartialLoader. Part 1. Need to be extended.
test($translatePartialLoader): add target API

A target API is added in comments
test($translatePartialLoader): rename delPart() to deletePart()
test($translatePartialLoader): rewrite tests

Tests for $translatePartialLoader are totally rewritten.
test($translatePartialLoader): remove methods from provider

Remove methods urlTemplate() and useLoadFailureHandler() from provider
test($translatePartialLoader): cooperation with $translate + little fixes

Fix ResolveErrorHandler: resolve a promise with an object instead of a string
Move $httpBackend verifications to afterEach sections
Change coding style according to the jshint
Fix some logical errors in the "Error handling" section
Add "$translate service cooperation" section
test($translatePartialLoader): fix variables

Change $provider to $translatePartialLoader
test($translatePartialLoader): fix http interceptors

Change $http request interceptors registration
test($translatePartialLoader): logic fixes

Little fixes in the test logic
feat($translatePartialLoader): Basic implementation

A basic implementation of the $translatePartialLoader service
chore($translatePartialLoader): coding style fixes
chore($translatePartialLoader): fix error throwing
chore($translatePartialLoader): fix error throwing implementation
chore($translatePartialLoader): merge namespaces from different parts

Now $translatePartialLoader can merge namespaces from different parts instead of
overriding them.

So, parts like
foo : {
  bar : "bar"
}
and
foo : {
  buz : "buz"
}
would result in table like
foo : {
  bar : "bar",
  buz : "buz"
}
instead of
foo : {
  buz : "buz"
}
Merge pull request #137 from DWand/service-partial-loader

Partial loader service