Service component - L3NM gNMI OpenConfig Service Handler:

- Added StaticRouteGenerator class
- ConfigRuleComposer: added dump methods to composer classes
- ConfigRuleComposer: extended configure methods to load previous configurations in devices
- ConfigRuleComposer: generalized to a single network instance for all static routing-based services
- ConfigRuleComposer: Updated static route organization with indexes and metrics
- ConfigRuleComposer: Added tracking of connected networks
- ConfigRuleComposer: Corrected config rule composer methods
- Integrated StaticRouteGenerator into Service Handler
- Multiple cosmetic improvements
- Added code for a future unitary test