Created general header file

A simple header that'll include all headers in your code
Moved all definitions to header

Decided to make this a header-only library, to simplify
compilation/linking
Updated headers to header-only library format

Moved all function definitions to the headers.
Added license

Forgot to copy the license boilerplate to Library
Merge branch 'beta' of https://github.com/hellocld/CLD-ECS into beta