[WIP] New repository structure

This is an attempt to give this repository the love it needs :)
During this point, there are three main groups for each functionality: `init`, `install`, `web-server`. 

I won't merge any existing PRs because I've already come too far with the new structure, sorry guys. On the contrary I will cherry pick them and add them by hand. The PR number will appear on the commit message.

When this is finished I plan to merge it with master. 

Please report anything you find that needs fixing or maybe an addition :)

### TODO
- [x] Move guidelines to a contributing.md file in root dir.
- [x] Think a way to address script naming.
- [x] Guidelines for scripts that do similar things. Which to keep.
- [x] Add description in each README of main subdirs.

### Pull Requests
- [x] systemd files #43, #14 
- [x] Improve apache virtual host configuration #50 , #79 
- [ ] github to gitlab migration script #44 
- [x] init.d script for centos 6.3 #58, #59 (check if this plays with version 5+)
- [ ] Check Debian/Ubuntu install scripts #81, #82, #107, #108 
- [x] CentOS init-script with rvm  #96 
- [x] Alternative solution for getting Nginx to work with gitlab on Centos #31 
- [x] Check CentOS installation #62, #102, #105 

### Remember to
- [x] Add reference links to systemd services
- [x] Add info about contributors in systemd services