New g:fzf_quickfix_open option

[ggustafsson]

Hello!

This patch add an option to disable the copen command inside of fill_quickfix() that several commands use. The default behaviour is good but it can get a bit weird when you already have several splits open (and I really like seeing just the (1 out of X): info status message) so I want to be able to disable it.

See it in action here: https://asciinema.org/a/511682

I just added a if statement with get() and tried to make everything fit in well. The code speaks for itself.

Best regards, Göran Gustafsson