Override ToolSectionLabel.to_dict so don't need to_dict_helper.
I feel this is cleaner and it makes ToolSection and ToolSectionLabel easier to move into a new module.
Various ToolBox filtering improvements and tests.
 - Allow overriding the base module location for ToolBox filters (needed for OS packages, etc...).
 - Allow scanning multiple base modules for filters.
 - Unit tests for module loading functionality, custom tool, label, and section filters, default hidden and require_login filters.
Move galaxy.tools.watcher into galaxy.tools.toolbox.watcher.
Remove lib/galaxy/tools/filters/examples.py likely incorrectly added in d816d66.
Move galaxy.tools.filters to galaxy.tools.toolbox.filters.
Leave empty module in galaxy.tools.filters and modify config to ensure backward compatibility (filters in this old directory will continue to work for now).

Update config/galaxy.ini.sample with more discussion of ToolBox filter.