feat(build runner): added in context, dockerfile_location

this is a new feature meant to allow people to use any file as
  a dockerfile and any folder as a context directory

test/test_api_usage.py

@@ -3852,6 +3852,7 @@ class FakeBuildTrigger(BuildTriggerHandler):
     prepared.subdirectory = 'subdir'
     prepared.metadata = {'foo': 'bar'}
     prepared.is_manual = True
+    prepared.context = '/'
     return prepared
 
   def get_repository_url(self):
@@ -4046,7 +4047,11 @@ class TestBuildTriggers(ApiTestCase):
                                                     trigger_uuid=trigger.uuid),
                                         data={'somevalue': 'meh'})
 
-    self.assertEquals({'status': 'success', 'subdir': ['/sometoken', '/foo', '/bar', '/meh']},
+    self.assertEquals({'status': 'success', 'dockerfile_paths': ['/sometoken', '/foo', '/bar', '/meh'],
+                       'contextMap': {'/bar': ['/'],
+                                      '/foo': ['/'],
+                                      '/meh': ['/'],
+                                      '/sometoken': ['/']}},
                       subdir_json)
 
     # Activate the trigger.