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
Removed libslic3r from the default include paths for all modules but
libslic3r. Now headers from libslic3r need to be included with an
explicit path (libslic3r/libslic3r.h etc)
Split the localization macros into I18N.{cpp,h}