Avoid playing directly with deliveries and reuse direct linking between
Software Installation and Computer.

Also move out error reporting from Computer to Software Installation.

It will be used to relate with Computer.

This document will represent state of installation software on computer.

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.