php7 syntax fix.
https://forum.dokuwiki.org/thread/15725
https://forum.dokuwiki.org/post/58606

The goal is to make the css replacement accessible in other contexts,
for example for the manifest.

typo

This adds some simple defaults for the guaranteed placeholders. This
ensures plugins can safely use these placeholders even when a template
did not implement them.

While DokuWiki suppresses PHP Notices they are still a code smell and
should be fixed. This fixes some PHP Notices that occurred.

Some of these fixes could be refactored into nicer code once we move to
PHP 7 and get access to the `??` operator.

This is important because the $cache->cache would have been set already and have no impact on the delivered result. Meaning: two different requests could have resulted in the same result.

Remove the flavour feature. It was some kind of a hassle. If you really want to filter out styles, you have to write a plugin either way and implement the tpl metaheaders event as well and handle everything your self.

The CSS modification is more like the JS_SCRIPT_LIST now. It adds some overhead, but not too much. It still gives great flexibility over the CSS.

Changed the cache initialisation: it does not use the list of files with an md5 (due to redundancy and time consumption) but the flavour and the type (previously removed).

Use the flavour system to create individual css files. Only the default flavour (style / style.ini) will have the default styles for interwiki and filetypes. There are two new events:

 1. CSS_STYLES_INCLUDED to modify the list of stylesheet files for a certain mediatype or prevent the mediatype or styles within it. This event is fired for the interwiki and filetypes too, to prevent that they are included
    * The Data that is being sent to the event contains: list of files or the keyword DW_DEFAULT for the interwiki / filetypes; the mediatype, the flavour, if the data should be encapsulated by a default @media and the encapsualation prefix (e.g. @media screen)
 2. CSS_CACHE_USE to prevent the use of a cached version of the CSS, just like the JS event that already exists.

Add flavours to template ini files. The template will now be checked for multiple ini files and inserts them as a custom flavours. The css.php can detect these flavours and reads the stylesheet + replacements from there. If the flavour is not the default one (style.ini), replacements are loaded from the default flavour first to ensure that the colours are available. Flavours can define their own set of replacements.

Remove type and caching mechanism. The cache will be checked later and the type will be replaced by an md5 hash of the list of style files.

use conf/tpl/<template-folder-name>/style.ini instead

This reverts commit de4634ec.

1 little fix

In an older version of PHP a file_exists() call would issue a warning
when the file did not exist. This was fixed in later PHP releases. Since
we require PHP 5.3 now, there's no need to supress any error here
anymore. This might even give a minor performance boost.

Added user*.less files to config

Otherwise comments are never visible in css.php

They are generated from the default ones and any additional one given
by the template. This allows to e.g. split admin styles from end user
styles in a closed wiki. You can then deliver only the user styles
using the metaheaders plugin.

This avoids treating double slashes as single line comments in CSS when
they are used in a filter or content string.

closes #638

Web path was used instead of filesystem one.

source maps are invalid for our dispatched sources and may even cause
problems. this makes sure any sourcemap declarations are stripped from
the output

for backwards compatibility

double slashes in url() always have to be ignored