add pytz to package dependencies
copy package tzlocal 1.0 (under the public domain) into scal2/lib
add zoneinfo-tree.json based on file list of /usr/share/zoneinfo
preparing for Time Zone: in core, ui and events (does not effect Occurence Views yet)
event_lib.py: add timeZoneEnable
event_lib.py: some cleaning
move timeZone and timeZoneEnable from Event to RuleContainer
event.timeZone implementation finished and looks working (should be tested better though)
add Etc to time zone groups, and read json file in order
time zone checkbutton tooltip