Bugids 70020, 70081, 64316, 96158 - help page link tweaks for video tools

The attached commits address four tickets:

https://wikia.fogbugz.com/default.asp?70020 and https://wikia.fogbugz.com/default.asp?70081 - Both the VET and the AddVideo tools had more or less hardcoded links to  help pages listing supported sites from which a user can embed videos. I created new messages which contain the help page URLs and replaced the hardcoded links with references to proper messages. This solution is more i18n-friendly because it allows the i18n team to customize where the links go to, which also resolves https://wikia.fogbugz.com/default.asp?64316. If they are not translated, they will still default to English. The last ticket - https://wikia.fogbugz.com/default.asp?96158 - requests for making the help page on open up in a new tab. A target="_blank" attribute has been added to the link.

I'm not sure about the syntax and if the commits are compliant with Wikia's coding practices, that's why I'd like to ask an engineer to review the code and if everything is ok - merge with the main branch or dismiss the request if it's not.Thanks in advance! :)