Special event processing for LastChange events

--HG--
extra : rebase_source : d79713bd55186a54bfc844a840da3ae49c083ca4
Fix for issue 201 of original SoCo (https://github.com/SoCo/SoCo/issues/201)
Checks that the SSDP search response contains the "Sonos" string, otherwise keep waiting for more responses.
Added a very simple example program that only displays the available players. This permits to test the zone discovery algorithm.
Clarified comments as requested.
Added sample Sonos SSDP response
A few adjustments to please pylint
Add crossfade
Remove code changes.  Replace with test/doc fix for cross_fade
Merge remote-tracking branch 'upstream/master' into crossfade

Conflicts:
	unittest/test_core.py
Make get_queue() return a SearchResult; add child_count to it.
Fixes for 'make lint'
get_queue: document max_items=0 and .child_count
Fixed formatting issue
More lint fixes
Removed useless else statement
More lint massaging...
Fixed unit test for discovery
fix
fix
fix
Merging with master