Plugins may want to add further fields to be present when saving drafts

This removes a lot of reudundant CSS classes in favor of cascading
selectors. Styling isn't done, yet this is just a first step.

Still to do:

* aria labels
* styling the toggle mechanism
* RTL styling
* making sure everything displays correct when no JS is available
* translations may be missing
* refactoring the rest of search.less to make use of LESS features

This functionality is inspired by what other large search engines are
doing.

This simplifies many aspects. However, it still needs much better
styling.

This add some search assistance to simple, single-word search queries
which may be restricted to a single namespace.

Further improvements:
* better styling
* trigger events for other plugins
* set namespaces directly from fulltext search results
* some more config options

If it's already inside an image tag, move the cursor to the end of the current tag.

The check did not work any more. see #1853

The file had 0 bytes before (starting from
5928c8e7) - probably something went
wrong while executing update.sh.

this also removes the non inified versions and incorporates some updates
the jquery CDN just pushed for jquery-ui

jQuery.browser no longer exists in jQuery nor in jQuery migrate. A quick
check in Opera and IE11 suggests that both parts that used it are no
longer needed so they were simply removed.

More browser tests especially for the resize handling in the media manager
are recommended.

The bind() call is deprecated in jQuery 3. This replaces it with
the on() call.

The delegate() call is deprecated in jQuery 3. This replaces it with the
on() call.

jQuery UI replaced the buttonset widget with a controlgroup widget. This
adjusts the JavaScript and styling accordingly.

- jQuery to 3.1.1
- jQuery UI to 1.12.1
- jQuery Migrate to 3.0.0

There are a few warnigs from migrate that have to be fixed. The toggles
in the Media Manager are also missing their proper icons.

checkfunc is mainly replaced by doku_hasTextBeenModified, which is put
in  global scope to allow overriding by plugins.

- if #wiki__text (the default DokuWiki editor field) exists, the
checkfunc() checks whether the field content is changed
- if #wiki__text not exists it assumes that on all change and keydown
events the content of the form #dw__editform is changed (give still
false positives.) (for example the Data plugin has none #wiki__text)

Fixes #1483

Fixes #1199

This drops support for Internet Explorer <9 which we no longer support.

The opera work around is still needed though! O_o