Various small code cleanups

* Use JobQueueGroup::push() in updateTitle().
* Made CurlMultiClient::request() return an array if no urls are given.
  Also cleaned up the options and error checking code a bit.
* Code style formatting.
* Added some type hints and make use of the 'self' keyword.
* Added some TODO/FIXME comments.

Change-Id: Iad4de0f0017b3f079971d76523d3a5a5487e9155