Extensible import formats

[bengtmartensson]

While the export formats mechanism is quite satisfying, the import formats cannot be extended. Extensible import formats can be implemented as XSLT transformations that take a user input to a Girr DOM, like the export format does (but of course the other way around.)

Related: #321.

Unclear how this is going to look in the GUI: A preprocessor combo box in Girr? (Most people will not find it there...) An "Other" pane?

[bengtmartensson]

A preprocessor combo box in Girr import. Preprocessor should be in XSLT (version 1) or an executable program, and produce valid Girr.