Added loadFont() and sourceURL feature for include()

This adds the `ejecta.loadFont()` function (that was absent in the Ejecta documentation just a few minutes ago).

The `sourceURL` is added for includes for proper file names in error messages. It also omits the `included` check (just like Ejecta proper) so you can create infinite include loops if you want to...

I'm not sure if I'm missing something by making `ejecta.include()` a proper function instead of the regexp replace!?

`ejecta.landscapeMode` was removed in the latest Ejecta version (again, outdated documentation, sorry).