Export SV in-game

[SafeteeWoW]

• The idea is to add an in-game command to conveniently copy saved variable in-game, instead of asking to upload SV, teaching howto, then waiting for SV every time. Uploading a saved variable file is not simple for most people.
• Mostly done. I am intended to let you write the description localed in RCLootCouncil:ExportSavedVariable() because I have no idea how you would like to do you. Besides, I have not add an command for it, but it's just two lines of code to call RCLootCouncil:ExportSavedVariable().
• Definitely paste the text of SV to Curseforge is terrible. Gist is a good place to go. No need to register before using Gist.

Most things to do:

• Besides the way to copy SV, we should also offer a convenient way to copy & paste website hyperlink to report the issue. I probably should allow more editboxes to be shown
• Catch LUA error of RCLootCouncil and when this happens, prompt user to report the issue.
• LootHistory can now use RCLootCouncil:ExportText(text, title, desc)
• WIP

[evil-morfar]

This PR has sat here for so long that it's become a mess of commits.

I still like the idea, but I'll probably extract the actual additions at some point when 3.0 development allows it.