Fix default websocket port detection in spice_auto.html

If server runs on port 80 or 443 the default value of
window.location.port is an empty string

Signed-off-by: Jordan Pittier <jordan.pittier-ext@cloudwatt.com>
Ack every message.

The failure to ack pings led to a nasty bug whereby an inactive client hangs.
The relatively recent change to monitor latency with ping exposed this bug.
Give the Garbage collector a clue to recycle images; avoids
fairly massive memory leaks during video playback.
Send the client cache size correctly in little endian order so we
don't claim to have an infinitely large cache.
implement and use a new dataview getUint64
Implement handling of SPICE_MSG_DISPLAY_INVAL_LIST

Also converts the display cache from an array to an object. This is to help enforce proper sparceness of the data as well as make it easier to reliably fully delete a given cache entry without affecting access to the remaining entries.
Add changelog for 0.1.4