Use system categories as filter options

Feature: Allow system categories to be used as filter options. Some bugfixes and documentation improvements. This version changes the database structure.

v3.0.0

Version 3.0.0 has lots of changes regarding TYPO3 9 LTS. It is not compatible with TYPO3 8 anymore (at least it has not been tested). For TYPO3 8 you can still use ke_search 2.X. A lot has been refactored (file names, namespacing, doctrince database access) which hopefully makes the code easier to read and maintain. Some features have been removed like indexers for obsolete extensions like tt_news and the "show score" feature. New features are logging, command controllers and fluid rendered preview images.

v2.8.0

[TASK] set version to 2.8.0

v2.7.0

[TASK] set version to 2.7.0

v2.6.2

set version to 2.6.2

Bugfix version, compatible with 6.2

Fixes https://typo3.org/teams/security/security-bulletins/typo3-extensions/typo3-ext-sa-2017-003/ for TYPO3 6.2 installations.
For 7.6 installations please use version 2.4.2 or above!