Multi-value number & text fields

True support for "multi: true;" property for Text and Number fields. Issue #13 .

I'm pretty sure it's hackish (to say the least). But seems to work fine, and looks like a pretty fundamental feature. Any suggestions appreciated.

Catches:
* Got an array with 10 000 values? Tough luck, that's how many input fields your browser will end up rendering (trying to render?).
* No fancy drag'n'drop re-ordering of values or anything even remotely similar.