Dockerfile: Fix checked-out branch ...

As is your dockerfile pulls the latest development branch, rather
than the last stable release. This patch:

  - adds an environment variable which can be used to easily change
    the pulled version (specifiying the tagged release)
  - Adds the command to `git checkout tags/<tag>`

Signed-off-by: Mark <mark@stengle.in>

Fix UPDATE_INTERVAL 300

Add php sockets

fix

Mini fix

Init