The v0.8 release contains a new extension, some features for others and bugfixes

A more detailed list of changes follows below. If you want to know the exact
and complete list of changes, you can check out the sources and check the logs.

Features:
* Triggers: Extensions can request to be the sole extension to be run
* Websearch: Order of fallbacks are now movable
* New extension: "System" , control your systems state

Fixes:
* Current screen. Remember window position. Closes #8
* Please allow fuzzy matching of spaces to underscores #40:
* Remember position if not centered. Closes #33
* Terminate application gracefully on SIGTERM. Closes #65
* Fix fuzzy. Closes #59
* Index text files too. Closes #60
* Drop unneccesary Qt5.5 dependencies. Closes #58
* Check if $XDG_DATA_DIRS exist. Closes #63
* Move after showing widget. Closes #66
* Terminate application gracefully on SIGTERM. Closes #12
* Escape Exec key string in dektop file. Closes #75.
