feat(router): add navModel.setTitle method
feat(router): add navModel.setTitle method

This is phase one of the changes needed to resolve #69, covering the API addition but no behavioral changes.

jods4/router,cmichaelgraham/router,alsoicode/router,bryanrsmith/router,bfil/router,aurelia/router,hitesh97/router,davismj/router,Roustalski/router,milunka/router,JeroenVinke/router,aurelia/router,StrahilKazlachev/router