[2.3] Enhancement: Real-Time resource alias field

This is a proposal to implement what was discussed here: https://github.com/modxcms/revolution/issues/11225

The alias field is a bit more complicated than the resource header (the big title), as it should reflect as good as possible what will actually be saved, which means I had to replicate the filterPathSegment() from the modresource.class.php method with all its regexes in JavaScript. Not all is possible (for example trim(regex) is a problem...thanks to IE8), but I'm quite ok with the results.

Tested:

- lowercase only yes / no
- maxlength
- restrict chars: alphanumeric, alpha, legal (=pattern), pattern
- multiple delimiters replaced by one

Looks like that:
![modx realtime alias](https://cloud.githubusercontent.com/assets/445501/3682463/7f987e9e-12cd-11e4-9202-3bd2243b9219.gif)