Add ability to specify config file for modx:install
Add ability to specify config file for modx:install

Currently, the required configuration options are passed through the command line during Gitify modx:install.
This prevents the installation process from being automated further, as described in #193.

To solve this, a physical config file can now be defined in the modx:install command as follows:
Gitify modx:install latest /absolute/path/to/config.xml

modmore/Gitify