sendError to propagate 403 up to servlet container.
notes about why this is so fucking strange.
Add error.html web-resource to handle generic servlet error-page muck
Add dispatcher REQUEST and ERROR to guiceFilter so that error page references can be resolved.
Merge branch 'master' into 401-error-page

Conflicts:
	components/nexus-core/src/main/java/org/sonatype/nexus/security/filter/authc/NexusHttpAuthenticationFilter.java
NEXUS-6123: Special validation for site.xml added
NEXUS-6213: Added log line when lax XML validation is used

As basically this means XML was detected as invalid, but
lax XML validation overrides that to "neutral".
NEXUS-6213: Laxed site xml path matching.
NEXUS-6213: UT

With positive and negative tests.
NX-156: fix REST-related split packages
NX-156: fix indexer-related split packages (excludes generated model classes)
Merge pull request #313 from sonatype/NEXUS-6213-site-xml

NEXUS-6213: Validation for Maven Site XML
NEXUS-6220: Expose method returning HC4 that supports keep-alive

To not have to fiddle with getting some RemoteStorageContext
Merge pull request #311 from sonatype/401-error-page

RFC: 403 error page
Merge pull request #314 from sonatype/NX-156-refactor-split-packages

REVIEW: NX-156: refactor split packages
Merge remote-tracking branch 'origin/master' into NEXUS-6220-conn-reuse
NEXUS-6220: Ask do we need connection reuse.

Before it was always "no". But, there are cases where
connection-reuse is needed, according to remote storage context
configuration.
NEXUS-6220: Adjusted Javadoc
NEXUS-6220: UT for reuseConnectionsNeeded method
Revert "Merge pull request #311 from sonatype/401-error-page" due to build failures (cause: error page cannot be webresource, as it accepts only GETs).

This reverts commit 75f0a0e0b9db99953a4aa3ec3c03a6750fa24e21, reversing
changes made to 7cbf810e804fa9a88c84b324275f9487fbd2f10a.
Change authz handling to allow 403 handling to filter up to jetty so that it can use servlets error-page.

Add a /error.html error-page to split out terse details.
Merge remote-tracking branch 'origin/master' into NEXUS-6220-conn-reuse