Now user have to set a destination to place a call. Fixed issue #85
Moved bill creation from GuiCustomerModificator to Customer class
Fixed issue #83
Also added total bill as sum of all calls in getBill method on Customer
class
Added comments on Pbes. Fixed Issue #72
Fixed getBill to get the total of all calls in a propper way
Deleted button pay. Fixed issue #81
missing javadoc comment for pBES functions. FIxed issue #80
Add comment on what button is meant when using the .get(NUMBER)
Fixed #86