Added new schema property removeDefaultNone which will prevent the addition of 'None' to select boxes when required is set to false

Added new schema property removeDefaultNone which will prevent the addition of 'None' to select boxes when required is set to false.

Fixes a problem when non mandatory selects require a default option with an internationalised string. For example the default might be:
'(use system default)'
Merge pull request #86 from Kirosoft/master

Added new schema property removeDefaultNone which will prevent the addit...