Moves some issue specs to work_package specs.
Renames Tracker to Type in lib, etc. folder

This includes data loader, pdf export, email and reminder Rakefiles, as
well as a few random places that I missed before.
Updates routes from Tracker to Type.
Changes translations of Tracker to Type.
Changes Tracker to Type in features.
Changes Tracker to Type in tests.
Changes Tracker to Type in fixtures.