#74 Add some validations support for attribute values

[Rakesh Kalra]

We need to think about the problem of validation errors
when updating the MBean attributes.

Simple validations like "int" can be performed by
looking at the data type, but application logic
validations are difficult to handle.

See the following thread for more info:
https://sourceforge.net/forum/message.php?msg_id=3627612