Fixes issue with incorrect characters in time strings on UI.
Fix platform dependency
Fix return value with incorrect strings.
Just use strptime and strftime on all platforms.
Emulate strptime on msvc... because they don't have it and their get_time is buggy.
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
