WifiDisplay: Add an HDCP toggle

Some WFD dongles have frequent (or permanent) failures while
negotiating HDCP with the device, so add a toggle to allow
skipping HDCP entirely

Change-Id: Ia70122d63aa76bcb91428152f588c4d6dd2b610f

Conflicts:
	res/values/strings.xml

Changes were already added to WifiDisplay.java in this
commit 844cf803c1234ec0f2f437516a6ca71ff3eff5d1