Added possibility for upload to Duet

Further changes:
- Added new configuration option Host Type
- Added abstract base class for future printer hosts
- Moved location of upload dialog (also made it a little bit more configureable)
- added possibility to send file via postfield instead a new frame

xs/xsp/typemap.xspt

@@ -270,3 +270,4 @@
 };
 %typemap{AppController*};
 %typemap{PrintController*};
+%typemap{PrintHost*};