[NEXUS-5651] Send 401 in case of an AuthroizationException and user not authenticated (not logged in)

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
[NEXUS-5651] Filter "/service/siesta/**" through  "noSessionCreation,authcBasic" filters

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
[NEXUS-5651] Introduce FilterChain, a mapping between path pattern and a filter expression

+ convenience guice module for easy binding

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
[NEXUS-5651] Map "/service/siesta/**" ->  "noSessionCreation,authcBasic" filters

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Typo nexus.anonynmous -> nexus.anonymous

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Merge pull request #800 from sonatype/nexus-5651-siesta-authz

REVIEW: [NEXUS-5651] Siesta resources authorisation