Adds SecFilterMappingMap - the collection of SecFilterMappings

It enables finding the mappings according to the filter's name and to
get set of URLs in which the filter is mapped to.

Signed-off-by: Mario Krizmanic <mario.krizmanic@gmail.com>
Adds the SecFilter that can be registered to FilterChainManager.

During the runtime it is resolved based on the url path matching in the
security context.

Signed-off-by: Mario Krizmanic <mario.krizmanic@gmail.com>