Added word cost feature to user dictionary

I added the word cost (not the connection cost) feature for the user dictionary. The last column represents the cost of its word.
If you have any comments or concerns, I would be very happy to hear them and fix them.

I have tested using the command `mvn -Ddownload=true package` and it successfully went through all the tests, including newly added tests.

Please do not merge yet (should preferably be after a future quick meeting).