All requested config values are written into SL1 ini file inside the zip
* TIme.hpp and Time.cpp is now part of libslic3r instead of libslic3r_gui
* Updated time manipulation function: separate timestamp_local_str and timestamp_utc_str
* timestamp_utc_str is used in header_slic3r_generated(). Gcode now contains UTC timestamps
A static symbol Slic3r::SEMVER is introduced, which holds
the running slicer's Semver object.
This is mainly done to make testing updater behaviour
_much_ easier. Additionaly to cleanup some questionable code
(Semver was being parsed multiple times / in multiple places
in the frontend.)
