simplify site build directory location
simplify site build directory location

using ${project.basedir} changes the location of target from
'slf4j-site/target/site' to start right in 'slf4j-site' so it only needs
to go back once.  This finalizes usage of project.basedir throughout.

b-cuts/slf4j,libliflin/slf4j,melezov/slf4j,b-cuts/slf4j,yukihane/slf4j,Andrew67/slf4j,nitinverma/slf4j,melezov/slf4j,lukecwik/slf4j,qos-ch/slf4j,b-cuts/slf4j,hazendaz/slf4j,libliflin/slf4j,lukecwik/slf4j,kbzod/slf4j,melezov/slf4j,libliflin/slf4j,nitinverma/slf4j,hazendaz/slf4j,Andrew67/slf4j,yukihane/slf4j,b-cuts/slf4j,qos-ch/slf4j,melezov/slf4j,kbzod/slf4j,yukihane/slf4j,qos-ch/slf4j,libliflin/slf4j,lukecwik/slf4j,b-cuts/slf4j,hazendaz/slf4j,kbzod/slf4j,Andrew67/slf4j,kbzod/slf4j,lukecwik/slf4j,kbzod/slf4j,yukihane/slf4j,yukihane/slf4j,libliflin/slf4j,nitinverma/slf4j,Andrew67/slf4j,lukecwik/slf4j,Andrew67/slf4j,melezov/slf4j,hazendaz/slf4j