core, add Numpad.qml file

Add a number pad file that creates a number pad of 5 numbers. The number
pad appears as a column
core, modify ActivityInfoTree.cpp and core.pri

Add the Numpad.qml and Balloon.qml files to the core.pri makefile.
Gcompris.pro: Add algebra_by activity.

Add the algebra_by activity to the GCompris.pro file and also sort the
activity fields by name.
Algebra_by activity: Commit all relevant files

1)Background image is stored in resources folder.
2)Edit the algebra_by/Activity.qml file to create the UI.
3)Update other makefiles.
4)Edit the activity.js file, though this is still incomplete.
core: Change NumPad.qml

Update NumPad.qml to include both the right-side
and left-side column in the same file.

Add a backspace button.
algebra_by activity: Update activity.js

Change the logical condition to retrieve operands.
Add conditions to validate the answer.
algebra_by: Update Activity.qml

Change the QML to accommodate changes made to NumPad.qml
Add condition to reset the operands if the child enters the correct
answer.
algebra_by: Update activity.js, Activity.qml

TODO: Fix level changing.
core: Update Numpad.qml

Use MouseArea instead of coordinates to detect click.
core: NumPad.qml: Replace "backspace" with "<-"

Use HTML hex code to replace the word "backspace" with the arrow.
algebra_by: Update activity.js

Remove the currentSubLevel() methos since it is not used anywhere.
algebra_by: Update Activity.qml

Fix operands refresh when level number is increased.
Try to add the "Iam ready" button feature

TODO:
Balloon time expired is not detected yet.
Fix "Iam ready" button.
Review code.
algebra_by: Update Activity.qml

Remove commented code.
Use ReadyButton.qml instead of creating a component here.
Fix balloon expiring.
algebra_by: Update activity.js file

Move questionsLeft() function from Activity.qml to activity.js
Remove some unnecessary variables.
Fix scoring mechanism
core: Update Balloon.qml

Fix display of bad bonus when balloon animation completes. To do this,
use onStopped signal but detct it ONLY when balloon completes a loop of
animation and not when balloon is restarted.
core: NumPad.qml

Remove commented code.
core: Add new file ReadyButton.qml

Create the Ready button element that contains the text "I am Ready!" and
add it to core. File gives a signal when the box is clicked.
Algebra_by improved.
core: Update core.pri with additions of new files

Add the new files ReadyButton.qml and Score.qml to core.pri
algebra_by: Update Activity.qml

Hide operands when previous level or next level buttons are clicked in
the middle of a test question.