Code improvement: view displays

[gklyne]

This list should probably be reviewed and broken out into sub-issues

• note that field selector field enumerations use the currently saved value of the target record type: dynamic changes in the form won't cause immediate updates to the selector drop-downs. Maybe this should be enhanced using Javascript and hiding values rather than suppressing them? (low priority)
• cross-field default values; e.g. field type defines default for value type via field description
• add "new field" logic to entity edit POST handler
• where possible, migrate methods from editentitybase to subclasses
• review logic - ideally, form handlers will access data from form, then hand off for processing