Changed validator for NewCLICommandDialog

[drpayyne]

Description

Changed validator for com.magento.idea.magento2plugin.actions.generation.dialog.NewCLICommandDialog

Fixed Issues

1. Change validation for the new CLI command dialog window #296: Change validation for the injection of new CLI command dialog window

Additional changes

• Created a new CliCommandRule to validate command CLI command formats
• Fixed bug wherein notEmpty validation doesn't work for a JTextArea field
• Moved isPHPClassValid() method from validator to main class to validate if the PHP class already exists.

Questions

• Would it be better to implement the logic of isPHPClassValid() inside the existing PhpClassRule class? We'll need to reuse this in various places
• Currently there's no validation to check if the CLI command already exists, just like a PHP class. I'm thinking this is needed since there can't be two identical commands doing different things. What do you think?

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with integration/functional tests (if applicable)
• All automated tests passed successfully (all builds are green)