Moved classes from package "org.leialearns.logic.common" to "org.leialearns.logic.prefixfree".
Moved class PrefixFreeBigIntTest from package "org.leialearns.logic.common" to "org.leialearns.api.common".
Refactored scala object PrefixFreeBigint to add method descriptionLength(BigInt):Int that shares a common internal method with prefixEncode(Bigint):String.
Extended scala test TestPrefixFree.