Renew the updater branch

Now with some actual consensus on what the updater will do!
Rework the update checking system
Implement DownloadUpdateTask

Installing updates is not implemented yet. That's next.
Implement update installer
Finish implementing update installation.

Also add the option to update on exit.
Added WIN32_LEAN_AND_MEAN

Should reduce compile times and help get rid of some error things.
Include shellapi.h in the updater on Windows.
Fix build failures on Windows.

* remove atoll
* fix include path of updater depends
Merge branch 'feature_updater' of github.com:MultiMC/MultiMC5 into feature_updater
Merge branch 'feature_updater' into develop
Merge branch 'develop' of github.com:MultiMC/MultiMC5 into develop