Master add README and additional documentation to TrigFastTrackFinder

Adds a README to the top directory of TrigFastTrackFinder and creates developer documentation in doc/TrigFastTrackFinderOverView.md. This MR also add comment strings for the declared properties in TrigFastTrackFinder.cxx and there has been some re-ordering of the property declarations to better group them to aid readability. A couple of issues to be followed with properties are flagged in the comments and a JIRA ATR-24242 added for follow-up.
None of these changes affect the running or output of the algorithm. There is in addition one change that changes INFO level printing in finalization to improve readability (the text was left over from when 3 numbers used to be printed, but only one is printed now).
This MR addresses the documentation JIRA ATR-24241