prepare RC5 : avoid fatal error with Views RC1 (we use views_handler_filter_float only if available)

#75423 followup - textfield widgets don't need the 'display:inline' part (that's only for number prefixes / suffixes)

(the 'validate' op is still supported, though)

Display field type human names instead of machine names on 'Manage Fields' and 'Fields' overview pages.

remove unneeded code ('tables' and 'fields' are always initialized as empty arrays - plus code was initializing the wrong element anyway)

- will confuse translators
- are not currently visible anyway

and content_update_6004 tries to add the indexes already created by content_update_1009

Mindworks-Networking (http://mindworks.hu)

split content_field_type_options($type = NULL) into content_field_type_options() and content_widget_type_options($field_type_name).
I've added static caching to both functions. This should be minimally invasive caching unless you're trying to insert new widget
or field types on the same page load the options are being displayed.

We can't trigger the menu_rebuild() ourselves here, too early.
node/content_types.inc's submit handlers take care of this after node types information has been rebuilt.

Since individual field config pages are secondary links, menu needs to be rebuild whenever an instance is removed.