To reduce user confusion, we were already presenting users with an error message
when they tried to edit constraints for bones from the Object Constraints tab.
This commit just makes things more convenient by adding a button which takes
users to the right tab when clicked.
- ability to change the space the axis is projected in (so you can choose worldspace or -space, was always local-space before).
- support projecting on a negative axis, without this some very simple clamping is not possible if the direction happened not to be positive.
- add distance limit (same as modifier), without this single meshes surrounding an object would make the constraint impossible to use in some cases (it would snap to the wrong side).
note: this removes the ability to project on multiple axes at once but this option only added up directions and didnt project on multiple axes as you might expect.
Notes:
* Made those edits by full checking of py files, so I should have spoted most needed edits, yet it remains quite probable I missed a few ones, we'll fix if/when someone notice it...
* Also made some cleanup "on the road"!
The code in this file is NOT restricted to use in object context only. Renaming
it makes it easier to find this file (taking in account name truncations).
