Improves customization of dock preferences

- namespaces preferences under 'sprout'
- adjusts multi-word attribute names to use underscores
- makes more of the attributes optional
- comments out some attributes to allow more of the default settings to be used.  But I left the comments in so that people would have a better idea of what could be done.
Merge pull request #196 from codeword/dockPreferences

Improves customization of dock preferences