New levels for algebra activities
This merge request adds new levels for additions/subtraction activities (algebra_plus/algebra_minus). Three levels are added:
- random operations with operands between 0 and 10
- random operations with operands between 0 and 15
- random operations where the result is between 0 and 100
- I made this in order to complete the set of levels in this activities (the actual set is based on operations table from 0 to 10).
The PR also brings some refactoring (impacts algebra_by/algebra_divide/algebra_minus/algebra_plus):
- the 11th level was implicit in the code (no level Data.qml for it). It generated 5 sublevels from previous level. Now, the 11th has its "special" Data.qml that constraints the operation generation.
And also small fixes:
- bonus appears on top of score
- sublevel counter is not increased when the level is finished