Tests: Add new classes to test.dc with the clrecv keyword for test_clrecv.
Tests: Write stateserver unittest for clrecv keyword.
Tests: Add cleanup to ss test_clrecv
Stateserver: Implement clrecv.
Tests: Fix ChannelConnection.clear_channels().
Readme: Add clrecv to the DC File documentation, cleanup the keyword descriptions
Merge branch 'clrecv'

Conflicts:
	test/testdc.py