* add button to open themes location to settings
botton creates directory if it doesn't exist yet
themes path is no longer hardcoded but included in settings
themes now default to None the default theme is no longer required
themes set to None will not look for empty directories anymore
this is backwards compatible
users with a nonexistant theme (Default) set will get the new None theme
* remove default theme from install instructions
* refactoring
* allow for creation of games as spectator
allow setting the amount of games per user to none
remove limit on amount of games when creating a game as judge as
spectator
* refactor common/server_player.cpp
* do not close games with spectating host automatically
* remove check that filters out 0 player games
this check didn't really do anything, deleted games are removed before
it would be reached
* don't transfer host to spectators
this seems to cause a bug, also present on master
* Run tests on Windows CI.
* Add message logger
* Skip tests that cannot be linked.
* Fix test call
* Fix mock link issue on MSVC
* Fix PATH variable to find libraries for tests
* Fail test step on test errors
