replace LESS compiler with 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
  ...

Translation update (uk)

The feed used to add real or fake email addresses to items (because some
feed formats require them). The default RSS1.0 format did not show them,
but that changed in the recent update of our FeedCreator classes.

Now all code for that has been removed, always showing an
@undisclosed.example.com email address. Because some feed readers may
use the email address to distinguis authors, the mechanism to prepend
the user name was kept.

small fix

Css modification actions - alternative

Add htmlspecialchars when showing $DATE_AT

#2021 broken links to W3C validators

Fixes #2061

also dokuwiki and php are on https

Translation update (sv)

doc fix

* results can be sorted by wanted or origin
* second dimension can be skipped
* results should be easier to parse with standard unix tools now
* use proper otpions, not commands

* 'master' of git://github.com/turnermm/dokuwiki:
  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

Create valid empty option in tpl_actiondropdown

Fix PHP Notices: Reduce error log noise

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.

The HTML-spec[0] specifies:

> If the element has no label attribute and is not a child of a datalist element: Text that is not inter-element whitespace.

So a non-breaking space is valid solution.

[0] https://html.spec.whatwg.org/multipage/form-elements.html#the-option-element

Translation update (fr)

Translation update (sr)

Translation update (sr)

Translation update (sr)