[Box2D] Clarity + Consistency improvements

[fernyrepos]

This is mainly for clarity and consistency within itself and other extensions. This extentions specifically gets a lot of questions i'll try to hopefully alleviate with better worded blocks.

• change "setup stage <>" to "set stage boundaries to <>" makes it more clear that this is just setting bounds
• add "to" back to the older physics properties properties (set bounce <>) is now (set bounce to <>)
• the confusing "touching <>" block is now a much more clear "list sprites touching <>"
• added "to" to the set scroll block for internal consistency and global consistency

[DNin01]

The documentation should be updated along eventually.