feat(router tabset): ability to configure routerLinkActiveOptions per tab

[sashaqred]

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• I read and followed the CONTRIBUTING.md guide.
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Short description of what this resolves:

Adds ability to configure routerLinkActiveOptions for individual tab. Config is merged with route tabset common config.
Also, adds NbRouteTab interface.

BREAKING CHANGE:
NbRouteTabsetComponent.tabs property type changed from any to NbRouteTab.
NbRouteTabsetComponent.changeTab property type changed from EventEmitter<any> to EventEmitter<NbRouteTab>.
tab parameter type of the NbRouteTabsetComponent.selectTab method changed from any to NbRouteTab.