[forms] the last touch: handle inlined relation forms as fields by introducing a simple InlinedRelationField. This makese things more flexible while removing a lost of overriding necessary.

fix label handling: when label is explicitly set to None, don't try to guess it

surrounding div necessary for proper error localization

cleanup base class

by default use new jquery widgets for Time/Date/DateTime fields

new jquery based widgets for Time/Date/DateTime, backported from crm

introduce a default render implementation on the base widget, which add_media and then call the newly introduced method _render(form, field, formrenderer), abstract of the base widget class. This allow a litle code factorisation and avoid to forget the call to add_media in subclasses.