[Feature] Use standard format for snapshot data

[xyzzy42]

TG uses a custom text based format to save the snapshots. This makes it hard to load the data into another program, like R or Python. These tools could be used to do a more sophisticated analysis of the data, such as a generating an Allan deviation plot.

Use a more standard format, such as jSON or XML, for the save data. This will make it easier to import, since libraries for reading it are common on virtually all platforms. jSON is also text based and should be comparable in efficiency to the custom format tg uses.