Reformat menu.cpp
Add getString and recognizeIntger methods to Menu
Replace getting integer input in Menu::start with 2 new helper methods
Add choosing window item to the main menu
Reformat manu.cpp
Add 0 as default return-value of Menu::recongnizeInteger
Change main menu unrecognized menu item error message to more readable
Replace getting integer input in Menu::addWindow with 2 new helper methods
Replace getting integer input in Menu::changePosigion with 2 new helper methods
Replace getting integer input in Menu::changeSize with 2 new helper methods
Replace getting integer input in Menu::chooseWindow with 2 new helper methods