Added static method that allows the deletion of a transaction from the
transaction list. this is used by the DeleteTransactionWindow.java
class. Also added a static save method that allows for the static
transaction list to be saved after a deletion. Added a variable called
total that keeps track of the current total of the transaction. Lastly
changed parameters of Transaction object to be doubles instead of
Strings
changed some class variables to be doubles instead of Strings, to allow
for easy handling of numbers. Added variables for month, day, year of
the transaction so it is easy to search for these attributes. Changed
the getTotal method to return double. Added getMonthDayYear method.
Changed toString so formatting of numbers with commas, $ only occurs in
the toString
Added a method to determine if user input is a valid double value. Also
added functionality to the SearchBtnListener which finds the appropriate
transaction that is to be deleted and deletes it.