Implemented and Tested `SessionStorage`

This storage is to be used inside the `SessionAuthAgent` in the future, as well as in any other Agents, which needs this kind of storage.
Implemented and tested InMemoryStorage to be used for SinglePageApplications
Refactored SessionAuthAgent in order to utilize new storages
Fixed SessionAuthAgent tests to work with new storage abstraction

Most of the tests were not working as expected before that change btw. The way the `sessionStorage` has been "mocked" is not possible the way it was done
Tested if default storage is created if none is supplied to the SessionAuthAgent
Added @implements documentation
Replaced SessionStorage by LocalStorage
CS: s/function()/function ()/g
Fixed JS doc to not use @implements tag
Rebuild CAPI with the new storage system