Fix client/server code separation for errai-security.

Move LoginPage and SecurityError to errai-navigation.
Fix SecurityRoleInterceptors so that the server class is not inheriting
form a client class.
Fix errai-security-demo and move it to the demo aggregator project.

Fix PageRequest import in errai-security demo.

Fix errai-security-demo (wasn't runnable).

Move errai-security demo to demo project.

Make errai-security-demo parent-less.

Fix plugin and deployment settings of errai-security-demo.

Add README to errai-security-demo.

Add errai-security-demo as module of errai demo aggregator.