sK1 file format model

During last week we have implemented sK1 document model which is fully compatible by interfaces with original native sK1 document. This issue resolves several important tasks. At first we got importing of reference file format. This will help to improve PrintDesign rendering. At second, we can start porting Skencil application to Gtk+ widgetset using MVP pattern. At third (and this is major issue) we can reuse a lot of code from UniConvertor 1.x and by this way we are going to release UniConvertor 2.0 at the end of May.