all user string input should be validated

[astubbs]

java.lang.IllegalArgumentException
	at org.jboss.forge.roaster._shade.org.eclipse.jdt.core.dom.AST.newName(AST.java:2420)
	at org.jboss.forge.roaster.model.impl.JavaSourceImpl.setPackage(JavaSourceImpl.java:625)
	at org.jboss.forge.roaster.model.impl.JavaSourceImpl.setPackage(JavaSourceImpl.java:53)

setPackage should do a notBlank check on user input and throw contextual exception (same for all user input methods)