Morphic and Tonel updates for Pharo 12

[JanBliznicenko]

Few more updates for Pharo 12+

• Fixes GeneralScrollPane no longer exists in Pharo 12 #356 - replaced use of GeneralScrollPane (that got renamed in recent Pharo versions) by code common to all Pharo versions
• Fixes Unify Tonel format #357 - moved all sources to Tonel 3.0 in order to limit commit changes noise
• Added few missing method protocols

[seandenigris]

I wonder if it's premature to move to Tonel 3 just yet. Not everyone will be on P12, and now those people presumably will have the same problem. I think someone said we can pin Magritte's Tonel version. Unless there is a Tonel 3 feature we desperately need here, I would prefer that.

[JanBliznicenko]

I wonder if it's premature to move to Tonel 3 just yet. Not everyone will be on P12, and now those people presumably will have the same problem. I think someone said we can pin Magritte's Tonel version. Unless there is a Tonel 3 feature we desperately need here, I would prefer that.

All right, makes sense, I will do that and re-do the PR.