[SPR-8240] Introduced new "Context management with @Configuration classes" section; fleshing out sections on context configuration inheritance and context caching.

[SPR-8240] Documenting TestContext support for @Configuration classes in the reference manual; and polishing the testing content in general.

[SPR-8240] cleaned up and formatted the testing chapter.

Updating references to @resource usage

removed reference to @Provider

SPR-7161
+ update Petclinic references
+ minor corrections

[SPR-5914] Updated reference manual to point out that class-level usage of @IfProfileValue overrides method-level usage.

[SPR-5640] Updated reference manual regarding new support for marking the test application context as 'dirty' after each test method within a given test class.