Merge pull request #6 from sschum/master

Some little changes
define addon-administration.properties as optional
add handler-method for filter action requests
Merge pull request #7 from sschum/osng-477

Osng 477
implements a redirect-builder and use them
add test for RedirectBuilder and fix them
UserService accept a parameter for "attributes" in searchUser
code styling
add tests for filtering
rename SessionData and move them into a subpackage
remove old SessionData class
save filter configuration into session and read from them
encode filter query
the RedirectBuilder can now handle single parameters
implements handling for userlist-sorting
fix testdata (user references to names)
fix test for multiple filtering in user-list
remove unused constructor
add Integrationtests for sort the user-list
implements limitation of user-list