refactor tail builder and add TailArray interface and implementations.
add index and builder package and move implementation classes.
modification affected by package move of tail classes.
Rank0 only sbv.
use Rank0OnlySuccinctBitVector for r0.
BitVector builder for LOUDSPPTrie.
test code change (affected from refactorings.)
refactoring.
add test for LOUDSPPTrie with sbv array index.
add some tests.
change default array size to 0.