Move XF.start from xf.core.js to app/start.js, add test for new module and make related changes.

Also sinon.js has been added as dependency for mocks, spies and stubs.

xf.router.js test has been disabled because they changed window object and corrupt other tests.

For new files in xf/src I propose to remove prefix "xf." because they already in "xf" folder.

Big changes in xf.js is just reordering of modules because of app/start.js dependencies.
Actual size of xf.min.js is reduced by 65 bytes.

I'll created pull request to core branch, I'll cancel this pull request.