[3.x] Add $titleLabel to BaseModuleController

[boonstoppel]

Summary

Currently it is possible to overwrite the "title" key for the "create modal" to something custom. This is done in the Controller (BaseModuleController).

For example:
protected $titleColumnKey = 'user_fullname';

When this is done the Label of said field will be displayed as "user_fullname", which is not very appealing.

It would be useful to be able to also overwrite the Label for that column key by either defining it like this:
protected $titleColumnLabel = 'User Fullname';

Or defining it directly as:

protected $titleColumn = [
   'user_fullname' => 'User Fullname'
];

[boonstoppel]

This label value could also be used as label for the column on the overview page where all data for that module is listed. By default that column is also title. When it is overwritten with $titleColumnKey you are currently auto generating that label eg. "user_fullname" becomes "User Fullname".

[boonstoppel]

There is also $titleFormKey, but it's unclear what that property does.