Allow bootstrap observing to be profile aware

[cspray]

Bootstrap observers could benefit from knowing what profiles are active. For example, a cache busting observer could be added that clears out any cached container definition before compilation in appropriate profiles, say 'dev' or 'test', but allows the cached definition in 'prod'.

In addition to adding this data on to the appropriate Bootstrap\Observer interface methods. We should also consider whether to allow configured observers to define what profiles they're active for since this seems to be useful enough to expose as a first-class citizen.