Refactor catalog package

 * Unexport internal structures
 * Add new access methods
 * Add mutexes
Split groups expansion methods by type

 * Use type-specific methods when expanding groups
 * Prevent non-matching metrics expansion on groups
Fix random group expansion failures

 * Add missing wait group
 * Remove catalog package dependency from library groups
Update CHANGES file for 0.2.2 release
Bump version to 0.2.2