This improves the filtering of issues and merge requests by creating a single file that encapsulates all the filtering. Previously this was done with a file for issues and a file for merge requests.
Created the ability for the text search to be done alongside other filterables. Previously because this was outside the filterable form, this wasn't possible and would instead do either filter dropdown or text filter - not both.
All inputs of type `search` will have the gray background
and search icon centered.
Because the search magnifier is a bg image,
I had to hide it with `[value=""]`.
I added a little javascript to make sure each input always has it's
own value.
