Write start log and preferences to code base directory

This is in addition to the user home directory & tracker subdirectory
and is useful when launching tracker from a USB drive, or
any case where TRACKER_HOME is not defined.
Fix bug: propertyChangeEvent causing wrong model to change start frame
restrict mass to minimum value 1.0E-30
Add minimum mass, fix setMass bug
Fix font sizer problems with titled borders
Add FontSizer code to enable setting font level
Add font sizing code
Add font level to preferences, more font sizing code
Tweak code related to font sizing
Set larger frame size when using higher preferred font level
Save and load table columns as displayed (not in default order)
Delete text column entries when deleting steps
Remove linked stylesheet references from all help HTML

Stylesheets are now controlled using Launcher.setStyleSheet() method,
enabling styles to respond to font level changes.
Restore help stylesheet references and add large font stylesheets
Add code to skip QT warnings when running on Vista
Add translucent grid overlay option to coordinate axes
Add more font sizing code
Enable point mass "boosters" to initialize dynamic models
Correctly enable track menu items (name, delete step, clear steps, etc)
Add boosters to particle model help