Revert "Exclude system site-packages from tests' sys.path"

This reverts commit fd4e4d814bdb3c643b678dd4f1d0bdf0fdfb00b0.

This commit changes the API/output of c.xmltestreport in a minor version without mentioning it. This essentially breaks every Jenkins job we have in coredev.
Revert "Back to development: 1.2.7"

This reverts commit 680d48f4e4aeca30dcb03a2acfd705b83147cc81.

Conflicts:

	CHANGES.rst
	setup.py
Update CHANGES.
Since we revert the API change in a minor version we should make a new major release this time for all users of 1.2.7 and 1.2.8.