Model "Tweet": table which relates every model.

1. created TweetsData for DB management; nowadays this class has these methods:

 - destroyTweet(String)
 - findTweet(String)
 - getTweets()
 - getTweetsWithHashtag(String)
 - getTweetsWithLink(String)
 - getTweetsWithUser(String)
 - getTweetsWithWord(String)
 - savetweet(String, String, String)
 - savetweet(Tweet)

2. Register the name "tweets" in the file file DbNames

3.  Model: the most reliable thing are these methods:

 - getGeoTweet()
 - getHashtags()
 - getLinks()
 - getUser()
 - getWords()
minnor refactor in GeoTweetData

- renamed getGeoTweets from getAllGeoTweets
- revised some javadocs
- moved one function
minnor refactor in HashtagData

- renamed findHashtag(id) from getHashtagById(id)
- revised some javadocs
- changed visibility of the contructor
Added functionality to WordsData:

- destroyWord(String)
- findWord(String)
- getWords()
- saveWord(String, GeoLocation)
- saveWord(Word)
Added functionality to UserData:

 - countUsers(AvaibleLocations)
 - countUsers(String)
 - destroyGeoTweet(String)
 - findUser(String)
 - getUsers()
 - getUsers(AvaibleLocations)
 - getUsers(AvaibleLocations, String)
 - getUsers(String)
 - saveUser(User)
 - updateCategoryToGeoTweet(String, String)
minnor refactor in LinkData

- renamed findLink(id) from getLinkById(id)
- revised some javadocs
- changed visibility of the contructor
Added new functionality to 2 models: "ArrayList<Tweet> getTweets()"

- Hashtag:
- Link:
Revision of "user" model: decided to remove the locationText due to pending integration of "TwitterNames"; genre field added.
Added functionality "ArrayList<Tweet> getTweets()" to word model; some refactor as code reorganization.
Useful method in Helper class. ArrayList<Tweet> castEachElementToTweet( ArrayList<Object> )
minor refactor changes in some files due to big refactoring in models and/or modelData classes.