Adding optional flags to show the full file paths in sourceLocation->file

[daskalou]

I found it useful to include full file paths as the sourceLocation->file field of each log entry (instead of just the filename).

Happy for you to include / change and merge if you think it's useful (and if not, no offense taken).

NOTES:

• I just copy and pasted from my local code into GitHub's code editor without testing to see if the changes I've made to your repo work properly (but they should).
• I haven't made any unit tests for this change, sorry (I've tested locally and it works fine for me though).