extendedSchema, bug fixes and adjustments

- Form mode adjustments in 'spfielControl' for lookup primary
fields. Force always to display mode.
- Adjusments in 'spfieldLookup'.
- Bug fix in setValidity for 'spfieldLookupMulti'.
- Bug fix in setvalitidy for 'spfieldUser'.
- Adjusments in 'spform'.
Now the controller 'setFieldFocus' method returns the focused
element.
Now after the 'validate' event and focus the invalid element,
broadcast a 'postValidate' event passing as an argument the
focused element.
- Adjusments in 'spformpage' directive of the module
'ngSharePointFormPage'.
- Implemented the 'extendedSchema' in 'SPFieldDirective' service.