Allow CLI options and arguments to get outsourced to config file

[a-r-m-i-n]

Currently it is not possible to define all options and argument in a separate file. This feature would change that.

Then, all options and arguments can get defined there and the call for EditorConfigCLI would be: vendor/bin/ec --config path/to/ec-config.php

Additionally it would be handy, if some of those options could get overwritten, by the actual CLI args. To unset already set options by CLI args, a new "unset" option becomes necessary. The possibility to override settings from new config file, should be disableable in the config file itself.

To make it more transparent and reliable, Editor Config CLI should provide a Configuration class, utilized by internals and by the outsourced configuration file.