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}
+ cleaned code from some global variables (App, AppConfig, PresetBundle, MainFrame, tab_panels..)
The XS was left only for the unit / integration tests, and it links libslic3r only. No wxWidgets are allowed to be used from Perl starting from now.
