Improve ctags support
Improve ctags support

* cleanup tag command
* add a tag-complete command
* add a gentags command for launching ctags in the background

Asenar/kakoune,rstacruz/kakoune,flavius/kakoune,danr/kakoune,jkonecny12/kakoune,Somasis/kakoune,danielma/kakoune,xificurC/kakoune,ekie/kakoune,flavius/kakoune,zakgreant/kakoune,occivink/kakoune,mawww/kakoune,jjthrash/kakoune,alpha123/kakoune,elegios/kakoune,occivink/kakoune,Asenar/kakoune,mawww/kakoune,ekie/kakoune,danr/kakoune,rstacruz/kakoune,lenormf/kakoune,danielma/kakoune,jkonecny12/kakoune,danr/kakoune,jjthrash/kakoune,jjthrash/kakoune,elegios/kakoune,Somasis/kakoune,alpha123/kakoune,casimir/kakoune,lenormf/kakoune,xificurC/kakoune,Somasis/kakoune,casimir/kakoune,jkonecny12/kakoune,danielma/kakoune,occivink/kakoune,alpha123/kakoune,casimir/kakoune,alpha123/kakoune,elegios/kakoune,ekie/kakoune,jkonecny12/kakoune,Asenar/kakoune,danr/kakoune,lenormf/kakoune,zakgreant/kakoune,elegios/kakoune,alexherbo2/kakoune,xificurC/kakoune,danielma/kakoune,ekie/kakoune,occivink/kakoune,zakgreant/kakoune,rstacruz/kakoune,Somasis/kakoune,flavius/kakoune,lenormf/kakoune,Asenar/kakoune,alexherbo2/kakoune,casimir/kakoune,alexherbo2/kakoune,rstacruz/kakoune,mawww/kakoune,xificurC/kakoune,alexherbo2/kakoune,flavius/kakoune,jjthrash/kakoune,mawww/kakoune,zakgreant/kakoune