composer updates

replace LESS library. fixes #4088

This replaces the abandoned fork with my own fork at splitbrain/lesserphp

That fork has been cleaned up somewhat and the issues in #4088 should be
fixed.

upgraded UniversalFeedCreator to v1.8.4.1

fixes #3651

updated composer dependencies

Merge branch 'master' into lesserphp

* master: (70 commits)
Release preparation
translation update
do not disclose email or IP addresses of users through RSS
small fix
Make default encapsu

Merge branch 'master' into lesserphp

* master: (70 commits)
Release preparation
translation update
do not disclose email or IP addresses of users through RSS
small fix
Make default encapsulation more readable and less duplicate.
Replace htmlspecialchars to hsc in core
Add the preview-bool for the cache file.
Add htmlspecialchars when showing $DATE_AT
#2021 broken links to W3C validators also dokuwiki and php are on https
made bin/wantedpage.php more flexible
doc abbreviation
Fix PHP Notices: Reduce error log noise
Create valid empty options
translation update
doc fix
translation update
using $options->getCmd to retrieve show-pages parameter
added option to wantedpages.php to show or not show pages where broken links occur
show pages where broken links occur: page_id => broken_link
clean extension names. fixes #2042
...

show more ...

use composer based library for feed creator #1970

updated GeSHi to 1.0.9.0

replace LESS compiler with lesserphp

This is a better maintained fork of lessphp. It seems to be fully
compatible, so this is more or less a drop in replacement.

switched geshi higlighter to composer based repository

added composer setup and the first composer package php-archive