ovs-bugtool: Add ovs-appctl dpif commands to debug bundle.

With single datapath, 'ovs-dpctl dump-flows ' dumps datapath flows for
all the userspace bridges in a system. It can get a little harder
to figure out the datapath flows belonging to a particular userspace
bridge.

This patch adds the 'ovs-appctl dpif/show' and 'ovs-appctl dpif/dump-flows'
output for each userspace bridge. This gives us a summary of configured
datapaths and all datapath flow entries for each bridge separately.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>