Resubmit: Addition of 'number' method/input type to Form Helper

Getting fed up of manually creating 'number' type fields in c5 forms! Now we can pass nifty 'min' and 'max' attributes to our input's $miscFields so decent browsers show a nice range clicker!
Merge pull request #1155 from arcanepain/patch-1

Resubmit: Addition of 'number' method/input type to Form Helper