Refactor draw tool and circle factory

[rafavalpa]

Divide circle create method in subfunctions:

• calculateMathShape

• createShape

• createLabel

Refactor draw:

• Rename global variable #started to #isDrawing
• Rename #start to #switchEditOrCreateShapeGroup
• Divide the method in #startShapeGroupCreation and #selectShapeGroup
• Add methods #setToNotDrawingState and #setToDrawingState
• Rename #update to #updateShapeGroupCreation
• Rename #finish to #finishShapeGroupCreation
• Create #emitDrawGroupCommand, #emitDeleteCommand and #emitMoveCommand
• Rename #setShapeOn to #setShapeListeners and move a part into #setMouseStylingListeners
• Create #getShapeFactory to contain a part of #setShapeListeners

[ivmartel]

Thanks @rafavalpa!