Export of the names of the SLA profiles was performed into the config bundle
for SLA profiles, which were nop set. A safe method is now used,
which stores an empty string in such a case.
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}
