Add support for immutable beans

See #11
Add clone() to all beans

Fixes #12
Add support for immutable beans - validation

See #11
Add support for immutable beans - toBuilder() method

See #11
Add support for immutable beans - toString() method

See #11
Simpler toString() generation
Add support for immutable beans - no FlexiBean support

See #11
Simpler toString() generation
Parse annotations above @PropertyDefinition

Fixees #10
Fix changes.xml