Meeting: changed getId() to getID() for consistency with Contact
ContactImpl: added overridden equals() and hashCode() methods for use in
ContactManagerImpl -- searching for notes on best practice led to the web
page commented in the code, which outlines the strategy followed here
MeetingImpl: see ContactImpl
fixed my silly error in thinking before -- of course past and future
meeting impls can extend meetingimpl like I initially wanted to, but only
if you remember to call the super constructor! shameful...
Inital commit of early progress in ContactManagerImpl public methods. I've
realised that there are going to be some quite frequently used checking
methods for dates, eg. isDateInPast(), etc that should probably go into
some other class. Likewise for the file reader/writer methods, but we'll
come back to those...