Panel improvements

[berycz]

1. other styles - bulma etc., now it's for bootstrap only

2. Panel.include and Panel.editable should somehow bubble down to descendants including fields, or the other way around, so we don't need to set that on both - Field and Panel

3. Panel.alert - when need - could support other bootstrap "options"

   • h4.alert-heading
   • icons
   • .btn-close