Added :FZFMruWindows to switch to Most Recently Used Windows

[AnuragNtl]

Hi, I'v added a bridge between FZF's :Windows and :FZFMru's :FZFMru. :FZFMruWindows can be used to switch between Most Recently Used Windows and Splits from all tabs.

[pbogut]

I'm not sure what should it be for, and how it should works. Could you explain a little bit what the purpose of this command is and whats the use case? It shows Tab / Win columns, but they change depends on which tab I'm at (even when tabs / windows / buffers didn't change). Sorry, I'm just confused.