7034: probably_alive() failing when no birth-death

Preparing to fix the bug:
refactor cut-n-paste traces in probably_alive, proper proxy access
minor bug with return_range handling
add testing ground

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps34@23005 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
7034: probably_alive() failing when no birth-death

ProbablyAlive.probably_alive_range:
If there is an existing death event without a recognizable date,
assume the death date to be "before today" for the calc purposes.

Tested with the repro database in the bug and the extra debugging.

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps34@23006 4ae1f11a-8b86-4847-b8af-ab372f36d1fd