TODO updated
Unnecessary print statement removed
Practice: new strengthener alg. and early practice

A new algorithm has been implemented for strengthening the words after
successful practice. An early practice page has also been implemented.

Notes:
- These features are currently available only for the 'hcs' user.
- They is not documented in the help page.
- "Show my future" works in the old way.
- The code implementing these algorithms should do more error-handling, and it
  should be better tested.