Data Tokens support

[NTaylorMullen]

Add data tokens and flow as part of our context objects

| 196 | 10410 | Reported By: Ryan Nowak |

[yishaigalatzer]

@rynowak are we thinking about utilizing this for attribute routing? If so please pull it in, otherwise i'm moving it out post Beta

[rynowak]

We should discuss next week. It's extremely likely we will

[yishaigalatzer]

We are not using data tokens for attribute routing

[yishaigalatzer]

Couldn't find a bug for this

DataTokens needs to be added to RouteData as a Dictionary<string,object>. TemplateRoute (and MapRoute(...)) need to accept data tokens from the user. When the route matches, the values should be copied to the RouteData.DataTokens

Also consider here making it IReadOnlyDictionary<string, object>

[Eilon]

The RouteData on the TemplateRoute that the user sets could very well be exposed as an IReadOnlyDictionary to someone inspecting it, but the RouteData that gets passed around in the RequestContext or wherever I think should be mutable, no?