Add the GIT_REV environment variable to /app/.profile.d

This allows child processes which might not have access to the
original environment to source the profile.d directory and gain
access to the information.
Removed docker-enter, we use built-in docker exec it also fixes problems with missing environment variables
Fixed dokku rebuild with specified revision
Fail if application is not built and we want to either release or deploy it, but when we do mariadb:link just inform the user and exit with 0
Cleanup application leftover images during deletion. It doesn't remove tagged images.
Just in case force to trigger ONBUILD hooks during release.
Merge remote-tracking branch 'origin/pr/76'
Use real revision instead of ref name: branch or tag
Fixes #81 with a little help from #82
Make exposed ports as configurable feature
Add information about application deletion
Added preliminary support for dokku-alt-manager
Added ability to generate self-signed certificate
Added information about dokku-alt-manager integration
Fixed help in dokku-alt-manager
Added mongodb:restart, mariadb:restart and postgresql:restart - special command to restart database container. However it doesn't restart applications which uses specified container
Enhanced dokku-alt-manager plugin: simple upgrade with specific revision
Just in case save successfully rebuilt revision as refs/heads/master
Don't show stderr when trying to determine version
Revert "Just in case save successfully rebuilt revision as refs/heads/master"

This reverts commit d3a81d9efe19e0eb6a108bf39ab957cd7b744fd7.