introducing OVSBridge
fallback to ovsb when no OF controller is unavailable
First crack at fixing multiple links

* Makes MultiGraph more like networkx.multigraph
* Adds converTo method
* Synchronizes node1 with xxx1 in link options
Allow natural sort to accept non-strings.
Allow Mininet() to accept multi-link topos w/correct params.
add example and test for multiple links
Minor fixes
Return (src, dst) in original order, and allow keys + data
Remove unused edgeinfo
Fix edges() and add convertTo() to Topo() (with keys option)
Ignore link info when sorting links.
Remove unnecessary 0
Merge branch 'fallback' of https://github.com/thinred/mininet into thinred-fallback

Conflicts:
	bin/mn
	mininet/node.py
Set VM date based on host date.

This should fix #398 for real; note that if we try to shut down ntpd
right at boot, it doesn't work! ;-(

However, setting the Unix time in the traditional manner using seconds
since 1970 should do the trick!
Don't check rt_runtime_us for CFS scheduler
Return controller correctly.
Raise exception if DefaultController cannot find a controller
Fix to allow more flexible version numbers
Draft update for Mininet 2.2b0
wrap the title string in quotes so that bash interprets it correctly