Add new method for converting user object

- method converts user to user with no emptyString values in object attributes
- use this in updateUser and updateNameTItles methods
- tested on postgreSQL and OracleDB
Merge pull request #302 from stavamichal/fix_update_user_for_oracle_use_null_instead_empty_strings

Add new method for converting user object

- method converts user to user with no emptyString values in object attributes
- use this in updateUser and updateNameTItles methods
- tested on postgreSQL and OracleDB