Updated test and added comments to testGetFutureMeetingListByContacts

Updated test, it now confirms that only one of the duplicate meetings is present in the returned list. Also checks an IllegalArgumentException is thrown when a non-existent contact is queried.
Added test for getFutureMeeting(Calendar date) method
getFutureMeeting(Calendar date) method passes new test
Rearranged tests, and expanded testGetFutureMeetingListByContact method

testGetFutureMeetingListByContact method now also tests two meetings on the same day, with the same contacts at different times. This test is done to ensure such a meeting is not considered a duplicate by the getFutureMeetingList(Contact contact) method.
Have written test for getPastMeetingList(Contact contact) method
Corrected some errors caused by copying and pasting
getPastMeetingList(Contact contact) method passes new tests