fixed the url tested against the double click vast plugin test
Merge pull request #711 from kaltura/2.12-Jun-29

2.12 jun 29
Merge branch 'master' of https://github.com/kaltura/mwEmbed
updated DFP test url to match default
Updated content api page removed hidden text, updated desc
Docs: don't jump up in the page when change media is called
fixed whitespace, makes simple php xml proxy much easier to read.
Support DFP try catch for ad request, give xml type to dfxp captions
added test file for playback interface type switch
Merge branch 'DFP-try-catch' into 2.13-July-13