Prevent entering invalid characters:
Now the user is not able to enter invalid characters to the NumericUpDown control.
An invalid character is defined as character other than:
* Positive/Negative sign (only if it is the first character)
* Number
* Decimal Seperator (only if there is none present)
Added listening to the Paste command.
If the pasted data is invalid then the command is canceled, otherwise applied to the NumericUpDown control.