Better Razor Compilation Diagnostics

This pull request moves the Razor feature in ServiceStack closer to a "first class citizen".

![Screen023](https://f.cloud.github.com/assets/478118/360509/867ba2a6-a198-11e2-98e8-f3d126690300.png)

This commit improves upon #561.

**Note: Only added support for the Razor2 project.**

The pull request has a check for `DebugMode` to prevent leaking sensitive data.

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@mythz, before I continue working on this ... I'd really like to refactor the entire Razor2 project. It's a complete mess with call traces everywhere. It took me forever to figure out who calls what and when and how and where. IMHO, it shouldn't be this complicated. Also, I'm starting get a whiff of some bad code smell in the way the everything is handled.

![Screen027](https://f.cloud.github.com/assets/478118/360530/1e32d960-a19a-11e2-98cb-304d304bcc93.png)

... perhaps start a new issue where we could discuss Razor2 refactorings?