Conversion Wrappers: Check for Valid Files/Folders

[astorm]

For example

* @argument unirgy_path Path to convert.php.php? [./convert.php]
* @argument m1_path Path to Magento 1 system? [./m1]
* @argument module_path Path to Modules to Convert? [./m1-to-convert]
* @argument desination_path Destination path? [./m2-converted]

Make sure conver.php exists

Make sure m1 looks like an m1 system

Make sure m1-to-convert has modules named correctly (top level folder, has a module folder, config.xml matches)

Make sure m2-converted looks like an m2 system (not true for code-migration)