lib/de_CH.po,lib/it.po,lib/sk.po: Minor translation updates.
src/printwx.cc: Default to exporting in the export format used last
time.
NEWS,doc/cad3d.sgml,lib/,src/: The "Sketch" vector drawing program
got renamed to "Skencil" some time ago, so update all references in
code and documentation.  cad3d has a new --skencil option to specify
this output format, but --sketch is still recognised for
compatibility.