add externalizable to Trie and relative class implementations.
Test code needs Java1.7.
make tries serializable.
add test for and debug MapDoubleArray.
move to org.junit.Assert.
make LOUDSTrie serializable.
fix bug.
add wiki file.
Merge remote-tracking branch 'origin/add-externalizable'

Conflicts:
	trie4j/src/org/trie4j/bv/BitVector.java
	trie4j/src/org/trie4j/bv/Rank0OnlySuccinctBitVector.java
	trie4j/src/org/trie4j/doublearray/MapDoubleArray.java
	trie4j/src/org/trie4j/louds/AbstractTailLOUDSTrie.java
	trie4j/src/org/trie4j/patricia/simple/MapNode.java
	trie4j/src/org/trie4j/patricia/simple/MapPatriciaTrie.java
	trie4j/src/org/trie4j/patricia/simple/PatriciaTrie.java
add comments.
add comment.
add comment.
add externalizable.
follow LapTimer change.
follow laptimer change.