add tail-index-array-packed TailDoubleArray
SparseArrayTailIndex experimental implementation.
refactoring patricia tries.
add dense array index class and refactor TailDoubleArray and TailLOUDS
tries.
Merge remote-tracking branch 'origin/refactor-patriciatrie' into
enh-refactor-tail

Conflicts:
	trie4j/test/org/trie4j/AllTries.java
	trie4j/test/org/trie4j/doublearray/TailDoubleArrayWithConcatTailBuilderTest.java
	trie4j/test/org/trie4j/doublearray/TailDoubleArrayWithSuffixTrieTailBuilderTest.java
	trie4j/test/org/trie4j/test/WikipediaTitles.java
refactor test classes (move package).
refactor tail classes (though bugs remaining).
code cleanup.
fix bug of indexCache0 of BytesSuccinctBitVector.
call trimToSize in build() method to reduce memory footprint.
fix bug that causes ClassCastException.
speed optimization(reduce comparison time).
reduce variable.
It is the knowledge of ArrayTailIndex that "-1" means "no index exists".
introduce TrieFactory for avoiding reflection overhead when measuring
time.
use PatriciaTrie for first Trie.
Merge pull request #7 from takawitter/enh-refactor-tail

Refactor tail array and introduce dense index array.