BAMPFA-79: Change how deferred calculation of decade/century start/end dates is done, to make it more robust.
BAMPFA-79: Add test for circa decade.
BAMPFA-79: Add toDisplayString method to Era.
BAMPFA-79: Clean up whitespace.
BAMPFA-79: Add program to parse a list of strings from a file.
BAMPFA-79: Add comment.