Add ability to create arc or pie shapes in addition to circles or ellipses.
Doc update
doc index: update
Update docs/source/user/index.rst
Update docs/source/user/index.rst
Docs update
Merge branch 'master' of github.com:gwaldron/osgearth
Update docs/source/references/symbology.rst
Update docs/source/references/symbology.rst
Update docs/source/references/index.rst
docs: symbology reference guide
docs
Update docs/source/references/symbology.rst
Update docs/source/user/features.rst
Update docs/source/user/features.rst
Add ElevationLOD range checking for FeatureModelGraph; add the feature_multilod.earth example for testing.
Merge branches 'master' and 'master' of github.com:gwaldron/osgearth
Merge pull request #282 from Thomas-Lerman/master

Arcs and pies from circles and ellipses
integraed MapNode-level Culling::CullUserData
Fixed rendering bug in graticules