Rename tutorials

[ddelpiano]

'Tutorials' menu
'tut1' -> 'Tut1: Simple cell network'
'tut2' -> 'Tut2: Detailed cell network'
'tut3' -> 'Tut3: Multiscale network'
'tut3_highip3' -> 'Tut3: Multiscale network' (high IP3)