[rlp-v2] Reconciliation of route selectors

[guicassolato]

The rules for reconciling RLP v2's routeSelectors (see RFC 0001) are:

• A route selector selects 1+ HTTPRouteRules
• For RLPs that target a HTTPRoute, all HTTPRouteRules in the HTTPRoute must be scanned for possible selection
• For RLPs that target a Gateway, all HTTPRouteRules in all HTTPRoutes pointing the Gateway as parent must be scanned for possible selection
• A HTTPRouteRule is selected when it contains at least one HTTPRouteMatch whose attributes include totally the attributes of the route selector
• For a set of attributes of a HTTPRouteMatch to include the attributes of a route selector, all attributes of the route selector must be explicitly and identically declared as the attributes of the HTTPRouteMatch
• While selecting a HTTPRouteRule, the HTTPRouteMatch may contain attributes that are not explicitly declared amongst the attributes of the route selectors – i.e., attrs(route selector) ⊆ attrs(HTTPRouteMatch), though not necessarily attrs(route selector) = attrs(HTTPRouteMatch)
• For RLPs that target a HTTPRoute, the set of attributes of any selectable HTTPRouteMatch implicitly includes the hostnames specified in the targeted HTTPRoute and all the hostnames of all Gateways pointed as parents of the HTTPRoute
• For RLPs that target a Gateway, the set of attributes of any selectable HTTPRouteMatch implicitly includes the hostname of the targeted Gateway and all hostnames of all HTTPRoutes pointing the Gateway as parent
• Hostname attributes specified in a route selector must as well be explicitly and identically declared in any of the instances above (HTTPRoute hostnames or Gateway hostname) that applies
• A route selector that finds no HTTPRouteRule with at least one HTTPRouteMatch including its attributes is considered invalid

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Related to: Kuadrant/architecture#13, #156
Follows-up on: #199.