Refactoring and fixes.

- File where to save data item is checked for each file separately. (Old
  versions had a bug that if there were data in save cache from multiple
  days (before and after day change), all data were saved to previous
  days file.
- Data datatype refactoring, values are stored now in double array,
  instead of storing them internally to serialized string.
- Memory leak fixes
- Refactoring
- TODO: Caching objects in Factory class, caching serialized data string
  until values are changed.

Signed-off-by: Mika Laitio <lamikr@pilppa.org>