Advanced forms behaviours

[mjashanks]

This is a collection of requested additions to forms. I may add to this.

Select - load options from external data sources

This mentions loading with new SQL Connectors aka Datasource plus: #1877

I have also had the request to

1. load options from a REST api
2. Apply a filter, based on other values on the form
3. Allow setting of a Value and a Display for the selected item

This also mentions filtering: #1617

We need to be able to trigger a filter, based on the value of a previous form field.

Custom validation

Should be able to provide more options for validation. I suggest that this should be javascript based. We need to be able to define rules like:
if 'Status' is 'Closed' then 'Closed Reason' is required
MinDate must be less than MaxDate
ClosedDate cannot be in the future

#1679
#1795

This should also give the option to write custom error messages so that:

1. The user can write a better explanation e.g. "When you set the status to closed, you must provide a reason"
2. Translation to other languages (see below)

Translation of validation messages

Currently, messages are always in english, users should be able to enter their own messages.

#1793
#2023
#1150

Control width of Inputs

#1895

Formatting of input values

e.g. allow currency symbols and thousands separators.

#1795

Using datepickers with external datasources

#1504

Multipage forms

#1062

Set default value on inputs

#1903

Multi-select picker

#1863

Clear form action

Ability to clear/reset a form on button click
#2043

Edit Form in a modal

I realise that this is stretching the scope of this a bit, but thought I'd list this in here anyway as it is related: #1199

[KernOil]

I'm looking forward to these improvements this will really make my app work great!