Setup; FSEmpty class first draft; FSBranch set up

No tests as yet
Cardinality; isEmpty; member in FSBranch class
A secondary branch const; draft of member
Initial drafts add, equal, subset
Remove, union drafts
Diff and inter drafts
scrap testing plan

working tests coming soon
some added comments; new thoughts on member, subset
some VERY INITIAL testing for runtime errors

...not correctness errors. all SEEM to be functioning except union and
diff
edited add method: remove mutation, redundancy
fixed up diff method

reordering and consolidating function calls; now reworking union
fixed up union method, no more runtime errors

now will start checking & proving correctness
3 property check funcs; random tree func

ALSO: just realized I have been committing but not syncing, oops!