[Mangos Zero] Install Guide Directory

[madmax]

Since we have a couple of guides showing how to compile and setup Mangos they will be linked here from now on.

• https://www.getmangos.eu/forums/topic/9136-rel21-temporary-compile-guide/#comment-74054
  This guide uses cmake and explains setting up the DB.
• https://www.getmangos.eu/forums/topic/9139-getting-amp-compiling-a-mangos-server-rel21/#comment-74060
  This guide uses the EasyBuild system and shows compiling the source and assumes you know how to load databases.