This helps to have compile errors when some
case it not handled while adding a new type.
The enum class can also be interated over
to create a complete drop down list.
An unspecified amount has also been added
to have the same semantics as before.
During these actions, the strings for title
and description of dialogs have been cleaned up.
1. Allow to change the date/time and
other relevant values of an event
on creation and after it was created.
2. Harmonize layout file names and
variable names.
