FAPI: Add form elements from D7 contrib that are now in core

[bugfolder]

In addition to all the form elements defined in system_element_info() (and text_format, which is defined in filter_element_info()), there are a bunch of form elements that are now in core and so should be added to Form API Reference:

From contextual_element_info():

contextual_links

From _date_element_info():

date_select
date_text
date_popup
date_timezone
date_year_range
date_combo

From options_element_info():

options

From field_ui_element_info():

field_ui_table

From file_element_info():

managed_file

From link_element_info():

link_field