Adding css styling option for help option in HTMLForm

There is now a new option named csshelpclass that can be passed in form
descriptors for HTMLForm objects.  This option accepts a css class and
applies it to the help text that is provided with the help option in the
form descriptor.

Bug: 65087
Change-Id: If1bd1d12a9159895f45c9cf0fbb7992e4c7e3526
Merge "Adding css styling option for help option in HTMLForm"