Split SubjectParser code in Application server specific classes

The SubjectParser contains package names for different servers within Strings.

This leads to some unmaintainable code.

Proposal (see also https://github.com/javaee-security-spec/soteria/issues/69#issuecomment-308394262) is to create separate maven artifacts with the application server specific code.

**Proposal**

- Interface with methods to retrieve caller and groups (getGroupsFromPrincipals, getCallerPrincipalFromPrincipals, ...)
- Server specific project contains an implementation of the interface which is defined as CDI bean. CdiUtils#getBeanReference(java.lang.Class, java.lang.annotation.Annotation...) can be used then to retrieve the implementation.