Added mistake counter functionality and applied changes to report it in the saved documents.

May still need some extentions based on more incoming info, currently only a very limited understanding of all that is needed. So there is limited functionality.

TestFiles/test res.txt

+tekst, latency
+This 00:00:00.180
+is 00:00:00.200
+an 00:00:00.080
+example 00:00:00.130
+sentence 00:00:00.190
+total latency: 780ms, average latency: 156.0ms, pairwise mistakes: 0