* changed collections in config container classes to final
* collections will be instantiated while container class instatiation.
* implemented add() method in config container classes
* changed call of add() method in using classes
* modified getter methods in config container classes to return unmodifiable collections in order to prevent direct write access to them
new class:
* QblPrimaryKeyPairTypeAdapter
new class:
* QblKeySerializationTest
-> test is not working yet as there is missing a proper equals() method for QblPrimaryKeyPair
Added equals method to QblPrimaryKeyPair and its contained classes:
* QblEncKeyPair
* QblPrimaryPublicKey
* QblPublicKey
* QblSignKeyPair
Made test for QblPrimaryKeyPair serialization working
Merge pull request #129 from f-porter/Issue108-Implement-add-method

Issue108 implement add method
Merge pull request #131 from f-porter/Issue130-Implement-QblPrimaryKeyPair-serialization

Issue130 implement qbl primary key pair serialization
Revert "Issue108 implement add method"
Merge pull request #141 from Qabel/revert-129-Issue108-Implement-add-method

Revert "Issue108 implement add method"
* implemented add() method in config container classes
* changed call of add() methods in using classes

* changed collections in config container class to final
* collections are instantiated during container class instantiation

* modified getter methods in config container classes to return unmodifiable collections in order to prevent direct access to them
Merge pull request #143 from f-porter/Issue108-Implement-add-method-new

* implemented add() method in config container classes