Fix continuous panel  issues and panning

Fix continuous panel issues :
- http://musescore.org/en/node/32191  Names on each staves
- http://musescore.org/en/node/32291  Staves of multiple instruments
- http://musescore.org/en/node/32206  Instrument names off-centered
- http://musescore.org/en/node/32201  Multi-line name instrument collide with stave
- http://musescore.org/en/node/32886 the last measure on the screen is moved under the gray rectangle