SimpleDateFormat now global in Defs.
Fixed wrong text on Invoice view. Updated texts.
Trimmed XML parsed strings.
Changed invoice layout cells alignment.
Added "fixed charges" invoice info.

The "services costs" are calculated as services_costs = total_no_vat -
discounts - fixed_charges. In case of XML formatting errors this will
fall back to set the "services costs" as 0.00. However, this might not
be a good idea!
Added Amount Dues information.
Fixed discounts calculations.

There are several discounts in the XML data we need to take into matter
when calculating the total discounts sum.
Fixed data counters for invoice downloads.
Invoice updates now added to checks and bandwidth stats.
Changes in invoice fragment behavior.

Invoice fragment now displays message if data is N/A.
Furthermore, if BigDecimal initializations fail due to unexpected XML
data the calculations will fall back to always use 0.00 as values. This
needs correction in the future. Better add an error message dialog
instead.
Added I/O calls to write/read data to/from internatl storage.
Downloaded invoices are now cached on the internal storage.

Downloaded invoice XML data (per profile) will be saved to internal
storage. Upon app load the last downloaded invoice data will be shown on
the Invoice fragment.
Updated HISTORY file info
Added IFragmentEvents interface connecting fragments.

First of all - this is a poor way to implement this. Must be refactored.
Currently the IFragmentEvents is implemented in BaseFragment that
supplies default impl. for each event call. The default impl. is just
doing *nothing*. The home and invoice fragments are connected to each
other via the IFragmentEvents when created in MainActivity. Each
Fragment decides to which event from the interface to react.
Fixed issue when deleting a profile.

The home and invoice fragments correctly did not get updated when a
profile was deleted.