#975400 follow up by bojanz: Give field::sanitize_value more power and fix some issues with get_value.

(reorder changelog)

#869172 by bendiy: Add an "external" parameter to field link rewriting so that external URLs can be formed properly even without a scheme.

#807616 by damz, dereine: Remove views_handler_sort_formula and add a short entry in api-upgrading.html

#1007730 by bojanz, merlinofchaos, dereine: Fix views_handler_filter_string, add tests and add a general placeholder method.

#972620 by dereine: Add an administrative title field for all handlers to make it more possible to distinguish similar fields from each other in the UI.

:q!

#927270 by Cyberwolf: Allow the "options callback" for the in_operator filter handler to also have an "options argument" in the definition.