Added and started the FindDueActivityForFriend screen, this screen will
display all the activities that this friend still has to pay for, and
the amount due for each of these activities. it might also later have a
small button next to each of these activities to directely pay for each
of them from your account but I am as of now unsure if I will implement
that, also added 2 methods to the com class that will be used, one
returns a string array that holds all the activities of a certain friend
and a second one simply counts how many entries there are in a array,
this is used to check if the friend is part of any activities
Chanched the FindActivitiesForFriend method in the com class to order
the activities based upon the date that the friend was added to them,
the oldest one first
Fixed the javadoc for the FindActivitiesFriend to explain better the way
that it sorts
Added all the methods needed to make the core of the
findDueActivityForFriend working, this includes finding the amount of
friends that an activity has and finding out how much  certain friend
has already paid for a certain activity. it should in theory now display
all of those amounts due, not really nicely just yet, but it displays
them at least
Included a small part that will calculate the total amount due and
display that
Included the newly made interface to the starter clas so that it can
actually run
Merge pull request #10 from Ylvakiller/FindDueActivityForFriend

Merging the FindDueActivityForFriend