Added "init.d" service script for Debian-based Linux.
Compatible with "/etc/default/gogs" configuration file for adding or overwriting values.
Based on "/etc/init.d/skeleton" and tested on Raspbian 2014-06-20 (Debian 7.5 [Wheezy] ARM)

[TO FIX] For some reason, it's necessary to remove the value of RUN_USER from the app.ini configuration file because the following error occurs:
2014/09/28 18:12:53 [setting.go:182 NewConfigContext()] [E] Expect user(git) but current user is:
Merge pull request #517 from silverkorn/dev

Added "init.d" service script for Debian-based Linux.
Fix #515
Debian's Init.d workaround for loading user's environment variables with `start-stop-daemon` command.
Implies 2 running child, so the `stop` command usually needs a `KILL` instead of a `TERM` to close properly so I reduced it to 1 second to get quickly with the `KILL` signal.
Merge pull request #519 from silverkorn/dev

Debian's "init.d" - Tentative to fix user's environment variables loading
Work on #516