Add feature: jumping to any file in the current solution

Simple API that, upon calling, retuns all files in the current
solution as QuickFixes. These can then be navigated in the editor to
jump to them like usual.

I'm hoping CtrlP will take good use of this! It's even better than ido
for emacs.

I'm also adding a feature for the emacs plugin where GotoFile and
currentfilemembersasflat will be called in succession. This should
allow for intuitive and fast navigation. I hope it will be easy to
implement in Vim as well, should you see the need :)