instead of hardcode

Conflicts:
	slapos/runner/views.py

For this, new constants defined: to choose if we want slapgrid-cp, slapgrid-sr,
both, and the maximum of tries

so they do not always lock the process until the end of slapgrid.
Moreover, they now only return True if slapgrid ends succesfully

Conflicts:
	slapos/runner/views.py

Conflicts:
	slapos/runner/static/css/styles.css

Conflicts:
	slapos/runner/views.py