SL-109 - added another diagnostic option for skel_tool.py. --slider_info dumps the info about bone-affecting sliders to stdout

SL-427 - trying less frequent computeBodySize() updates to avoid 'camera at sea' and related issues.

MAINT-6647 - make SLM behavior still available if MeshImportUseSLM is true; still defaults to false.

MAINT-6647 - ignore previously created slm files on model upload. SL-442 - change coloring for show bones, to highlight joint positions and rigging

The CMake invocations are controlled by UNATTENDED -- these were not. Let
CMake do it if it must be done.

VSTool manipulates the SecondLife.sln solution file for the convenience of a
developer subsequently running Visual Studio interactively. But the cost of
having it sometimes break TeamCity automated builds is too high -- especially
since we never expect to run Visual Studio interactively on a TC build host.

Also remove the CMake UNATTENDED variable that controlled it.

MAINT-6631 - reluctantly, added support for animation of collision volumes, to avoid breaking existing content.

SL-109 - made viewer much less tolerant of bad data in avatar_skeleton.xml or avatar_lad.xml. If either of these is broken, there's no point trying to continue, more informative to just error out with an appropriate message.

SL-433 - fix for mesh eye scaling with eye size slider. Previous values were based on incorrectly sized reference eyes.

The only call to the findDiscardLevelsBoundaries() method was commented out
inside initDecode(), with a comment:
        // Merov : Test!! DO NOT COMMIT!!

This was the only caller of copy_tile(), which was the only caller of
copy_block(). Commented out all three of these (biggish!) functions, since I
have no idea what any of them were supposed to do or when it might be useful
to call them. In other words, I can't yet rule out the possibility that I
might have to uncomment them.