utf path support

[youyialex]

Hi there cboulay, I'm having a problem with saving data file when the path contains Chinese characters using LabRecorder-1.16.4-Win_amd64. It behaves as follows:

1. when the dir includes Chinese characters, xdf file could not be created and the file size keeps displaying 0Kb in the status bar;
2. after changing the path which only include ascii characters, the file could be created.

Seems like it's a problem relating to non ascii characters in path under windows.

[youyialex]

FYI: the system locale on my PC is Chinese(Simplified, China).