submitHelper module

Fixes #1830 

Takes over `uncheckSendRepliesToInbox` functionality from betteReddit.

Currently the repost warning box is styled with reddit's classes (so it could potentially be mistaken for native functionality). Is it enough to make the feature disabled by default, or should it be more obvious that it's a feature of RES and not reddit?
I also had to remove the ability to search the text of self-posts to reduce false negatives, but I don't think that's too big of a deal.
Looking for critique / improvements of this regex (designed to remove unimportant parts of URLs so that we can compare them). Here are a few test cases to illustrate what it does right now:

    http://www.youtube.com/watch?v=A8JsRx2lois&feature=youtube_gdata_player#t=58s -> youtube.com/watch?v=A8JsRx2lois
    https://en.wikipedia.org/wiki/Regular_expression#Basic_concepts -> en.wikipedia.org/wiki/Regular_expression
    http://jarkko1.deviantart.com/#/d5d2l2v -> jarkko1.deviantart.com/#/d5d2l2v
    https://www.reddit.com/r/pics/comments/92dd8/test_post_please_ignore/.compact -> reddit.com/r/pics/comments/92dd8/test_post_please_ignore
    https://i.imgur.com/ppBPV.jpg -> imgur.com/ppBPV
    https://www.reddit.com/r/Breadit/search?q=bread&restrict_sr=on&sort=relevance&t=all -> reddit.com/r/Breadit/search?q=bread

My only concern right now is removing everything after the the first `&` - this is pretty much necessary on sites like youtube that will often have different URLs for the same video, and only the first part of the query string is important (as above). However, there may be sites where this will result in false positives.