Add a variable wxfilename which holds the filename of the document.
Images in wxmx files are in png (required for wxwidgets 2.9).
Set the working directory when loading a maxima document.

Fixes #218.
Translating new lines to Hungarian.
Increase version.

Fixes #255.
Merge branch 'master' of ssh://git.code.sf.net/p/wxmaxima/code