New Functionality 
1. Added the ability to display segment axes.
2. Added option to set default pose from GUI.
3. API: Now available components including BushingForce as well as a 
SpringGeneralizedForce.

Documentation:
1. Updated Developers' Guide and plugin example

Bug Fixes:
. Bug 1068: Can't interrupt running tasks.
. Bug 1065: Crash previewing motion data files
. Bug 1140: Distorted display of muscles wrapping around a sphere.
. Bug 1124: Problem parsing xml elements that use no closing tag.
. Bug 1110: Old model (before 1.8) can't be opened.
. Bug 1069: Crash when restoring a muscle from GUI.
. Bug 1045: Scale Tool does not preserve locking and clamping.
. Bug 1041: Crash trying to change the type of a muscle point.
. Bug 998: Plotting quantities with identical column headers is
problematic.

Notes:
1. Platform dependent libraries are included, depending on user's 
development environment, the corresponding binary distribution is 
required. This is relevent only to API users. GUI users can use any
distribution.. API release on Mac OSX, Linux