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
Fix default_data_quota module

- before this fix could be dataQuota set to unlimited even if limit was not unlimited
- now dataQuota can not be unlimited if limit is still limited
Use to_timestamp instead of to_date function for PostgreSQL for tasks and tasks_results tables
  - added toDate function to Compatibility
  - modified DAOs in tasks-lib to use the compatibility function
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
Merge pull request #307 from stavamichal/fix_default_data_quota

Fix default_data_quota module

- before this fix could be dataQuota set to unlimited even if limit was not unlimited
- now dataQuota can not be unlimited if limit is still limited
Merge pull request #322 from mvocu/michalv-date-to-timestamp-fix

Use to_timestamp instead of to_date function for PostgreSQL for tasks and tasks_results tables