Optimisation, fixe some bugs, add some comments

[pprados]

• I use K or V in place of Object in containers
• It's not acceptable to have a System.exit(). I convert the code to throw a HeapCorruptedError exception.
• I change the version type in header from int to long, and set with the serialVersionUID, after add a Serializable in the generator and generated classes
• I add the annotation @PersistentObject in each persistent object ;-)
• I add a cache in typeForClass() and add a strategy for Scala code
• I change the constructor of PersistentObject to be compatible with Scala
• I remove some unused import
• I add some @Override

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