Allow FXFormFieldTypeOption fields to work again

Sorry, introduced a bug in the FXFormOptionPickerCell branch that turned regular
FXFormFieldTypeOption fields into FXFormFieldTypeDefault fields.

This PR fixes that problem
Merge pull request #24 from bartvandendriessche/fix/broke_regular_FXFormFieldTypeOption

Allow FXFormFieldTypeOption fields to work again
Code tidying
Added support for block-based actions
Added placeholder value
Picker and date picker now display correct value when re-opened