Reorganization of the menu

[Johnny Jazeix]

Hi,

Mostly thanks to Isabelle, we did an improvement on the menu to better
distribute the activities by section and by content.
So we now have the following sections with categories:

* computer
baby_wordprocessor, erase, erase_clic, clickanddraw, clickgame,
followline, erase_2clic, penalty, ballcatch, mining, babyshapes,
gletters, smallnumbers, wordsgame

* discovery
    - logic
railroad, algorithm, graph-coloring, sudoku, superbrain, hanoi,
hanoi_real, traffic, fifteen, lightsoff

    - fine arts
details, paintings, explore_monuments

    - music
instruments, explore_world_music, memory-sound, memory-sound-tux,
play_piano, melody, piano_composition, notes_name, play_rhythm

* experiment
    - sciences
explore_farm_animals, explore_world_animals, canal_lock, watercycle,
binary_bulbs, color_mix, color_mix_light, intro_gravity, land_safe,
renewable_energy, solar_system, submarine, digital_electricity

    - history
family_find_relative, family, chronos, roman_numerals, louis-braille

   - geography
geocountry, geography

* fun
memory, memory-tux, football, hexagon, photo_hunter, balancebox,maze,
mazerelative, mazeinvisible

* math
    - numeration
drawnumbers, smallnumbers, memory-enumerate, planegame, reversecount,
smallnumbers2, enumerate, memory-wordnumber, number_sequence,
numbers-odd-even, guessnumber

    - arithmetic
magic_hat_plus, memory-math-add, memory-math-add-tux, algebra_plus,
gnumch-equality, gnumch-inequality, target, magic-hat-minus,
memory-math-minus, memory-math-, minus-tux, algebra_minus,
memory-math-add-minus, memory-math-add-minus-tux, memory-math-mult,
memory-math-mult-tux, algebra_by, gnumch-multiples, share,
memory-math-div, memory-math-div-tux,algebra_div,
memory-math-mult-div, memory-, math-mult-div-tux,
memory-math-add-minus-mult-div, memory-math-add-minus-mult-div-tux,
guesscount, gnumch-factors, gnumch-primes

    - measures
scalesboard, scalesboard_weight, scalesboard_weight_avoirdupois,
money, money_back, money_cents, money_back_cents, clockgame, calendar,
find_the_day

* puzzle
paintings, leftright, tangram, mosaic,crane , redraw,redraw_symmetrical

* reading
    - letters
baby_wordprocessor, drawletters, click_on_letter_up, click_on_letter,
memory-case-association, memory-case-association-tux,
alphabet-sequence, gletters, braille_alphabets, braille_fun

    - words
wordsgame, letter-in-word, missing-letter, readingv, readingh,
imagename, hangman

    - vocabulary
colors, babymatch, categorization, lang, advanced_colors

* strategy
bargame_2players, bargame, tic_tac_toe_2players, tic_tac_toe,
align4-2players, align4, nine_men_morris_2players, nine_men_morris,
checkers_2players, checkers, chess_2players, chess, chess_partyend

Johnny