Remove capistrano, can still be used at mconf/mconf-web-caphub

Deploy with capistrano is now made using caphub, see
https://github.com/mconf/mconf-web-caphub

cherry-pick 02d7a7f784, conflicts:
	Capfile
	Gemfile
	Gemfile.lock
	config/deploy.rb
	config/deploy/conf.yml.example
	config/deploy/production.rb
	config/deploy/staging.rb
Remove old installation scripts, refs #638

They are not used anymore, installation now only via wiki or capistrano, see
https://github.com/mconf/mconf-web/wiki/Mconf-Web-Deployment

cherry-pick 223037efbaa98e