Design Add and Search Words Data Structure 
Design a data structure that supports adding new words and finding if a string matches any previously added string.

Implement the WordDictionary class:

1. WordDictionary() initialize the object.
2. void addWord(word) Adds word to the data structure, it can be matched later.
3. bool search(word) Return true if there is any string in the data structure that matches word or false otherwise. word may contain dots '.' where dots can be matched with any letter.
Example: 
Input
["WordDictionary","addWord","addWord","addWord","search","search","search","search"]
[[],["bad"],["dad"],["mad"],["pad"],["bad"],[".ad"],["b.."]]
Output
[null,null,null,null,false,true,true,true]

Explanation
WordDictionary wordDictionary = new WordDictionary();
wordDictionary.addWord("bad");
wordDictionary.addWord("dad");
wordDictionary.addWord("mad");
wordDictionary.search("pad"); // return False
wordDictionary.search("bad"); // return True
wordDictionary.search(".ad"); // return True
wordDictionary.search("b.."); // return True