save getters for already recorded properties
add withCopyMethod to GeneratePojoBuilder

When withCopyMethod is true, a special method named copy will be generated.

This method allows you to easily create a new object that is identical to another object.

That is especially helpful, when you want to create a new object from an already existing immutable object, that has only a few fields that differ.
add examples for withCopyMethod
Merge branch 'master' into copy-method-2

Conflicts:
	src/main/java/net/karneim/pojobuilder/BuilderModelProducer.java
	src/main/java/net/karneim/pojobuilder/model/BuilderM.java
	src/main/templates/Builder-template.stg
Merge branch 'master' into copy-method-2

Conflicts:
	src/main/java/net/karneim/pojobuilder/BuilderModelProducer.java
	src/main/java/net/karneim/pojobuilder/model/BuilderM.java
	src/main/templates/Builder-template.stg
Merge pull request #27 from simonwagner/copy-method-2

generate copy method