WICKET-5694 Add WicketTester assertion methods for component's markup style, variation and locale

(cherry picked from commit b09593a6e1f60b080e2f27d739336757ec01d686)
Upgrade Spring to 4.1.0
Remove useless javadoc (@see interface)
Provide simple implementation for few methods of ApplicationContextMock
WICKET-5689 Nested Redirects and REDIRECT_TO_BUFFER

(cherry picked from commit b5b2c9d10e6ae1df0e44a5448558da285d0cea99)

Conflicts:
	wicket-core/src/main/java/org/apache/wicket/request/handler/render/WebPageRenderer.java