Add dokku ebuild

[aegypius]

dokku

• [x] Replace "install" hook by portage install procedures
• [x] Handle buildstep building in src_compile if buildstep use flag is on

  nginx plugin

• [x] Handle "install" hook for nginx plugin
• [x] Add support for systemd
• [x] Warn if /etc/sudoers.d is not included in /etc/sudoers
• [x] Suggest nginx conf if not using nginx config layout

  Community plugins ebuilds

Providing packaged plugins based on Dokku Plugins Wiki

• [x] app-emulation/dokku-plugins-meta

  Datastores :

• [x] app-emulation/dokku-plugin-mariadb : https://github.com/Kloadut/dokku-md-plugin
• [x] app-emulation/dokku-plugin-postgresql : https://github.com/Kloadut/dokku-pg-plugin
• [ ] app-emulation/dokku-plugin-mongodb : https://github.com/jeffutter/dokku-mongodb-plugin
• [ ] app-emulation/dokku-plugin-redis : https://github.com/luxifer/dokku-redis-plugin

  Process Managers :

• [x] app-emulation/dokku-plugin-supervisord : https://github.com/statianzo/dokku-supervisord
• [x] app-emulation/dokku-plugin-shoreman : https://github.com/statianzo/dokku-shoreman

  Other :

• [x] app-emulation/dokku-plugin-rebuild : https://github.com/scottatron/dokku-rebuild
• [x] app-emulation/dokku-plugin-link : https://github.com/rlaneve/dokku-link