[UNDERTOW-466] Split the SecurityContextImpl in two.

[darranl]

Split out the generic notification handling side of the SecurityContext implementation into an abstract base class so future SecurityContext implementations can focus just on the actual authentication.

Note: I have chosen not to add the deprecated methods to the abstract class as I believe once Java 8 is available it will be better to handle them on the interface to make implementing those methods entirely optional.

[undertow-pull-request]

Windows Build 1191 is now running using a merge of fe2b72e

[undertow-pull-request]

Linux Build 1471 is now running using a merge of fe2b72e

[undertow-pull-request]

Windows Build 1191 outcome was FAILURE using a merge of fe2b72e
Summary: Tests failed: 4 (2 new), passed: 2503, ignored: 375 Build time: 0:13:26

Build problems:

Failed tests detected

Failed tests

io.undertow.websockets.core.protocol.WebSocket08ServerTest.testCloseFrame{proxy}: <no details avaliable>

io.undertow.server.handlers.proxy.LoadBalancingProxyAJPTestCase.testStickySessions{proxy}{spdy}: <no details avaliable>

io.undertow.server.security.SpnegoDigestAuthenticationTestCase.testDigestSuccess: <no details avaliable>

io.undertow.server.security.SpnegoDigestAuthenticationTestCase.testDigestSuccess{proxy}{http2-clear}: <no details avaliable>

[undertow-pull-request]

Linux Build 1471 outcome was FAILURE using a merge of fe2b72e
Summary: Tests failed: 2 (2 new), passed: 2582, ignored: 298 Build time: 0:15:25

Build problems:

Failed tests detected

Failed tests

io.undertow.server.handlers.proxy.mod_cluster.StickySessionForceUnitTestCase.testDomainNodeInError{proxy}{https}: <no details avaliable>

io.undertow.server.handlers.encoding.EncodingSelectionTestCase.testEncodingSelectWithQValue{proxy}{https}: <no details avaliable>