Support new date format

[sw]

I don't know if this has been fixed already.

I'm using the Android app version 1.12.0 in combination with XCTrack 0.7.0.4

It seems that the new XCTrack app saves the date in the new format which IGC Viewer doesn't support. The flights show up with a date like "DA/TE/:080718,01" for 2018-07-08.

See http://vali.fai-civl.org/faq.html -> search for DTE

Please also consider showing the date in a non-confusing format such as ISO8601 (YYYY-MM-DD)