Conflicts:
	slapos/grid/slapgrid.py
	slapos/tests/slapgrid.py

Add periodicity and factored tests

Fix 77bc6c75

Also use this code in test.

It will be used during allocation.

Allow to add new networks. Allow to associate Computer into networks. Allow to
see list of Computers in network.

Each iteration (each partition) of main CP loop has sanity checks and makes sure nothing raises outside.

This reverts commit aa0ba0cf.

Sometimes, git default merge strategy is really dumb. Or it may be me.

Conflicts:
	slapos/grid/slapgrid.py

If partition is not processed correctly, it's good to know what instance it is.

Add tests to ensure master is not called when using common Computer methods with empty computer_guid

Just doing it by factoring code.