entitry is only viewable when the classes are shown

should fix #744
Installation of postgresql-9.3 documented.
Merge pull request #754 from ontohub/744-show_only_entity_tree_when_it_should

entitytree is only viewable when the classes are shown
add beta label
Merge branch '747-label_as_beta' into develop
Merge branch 'develop' into develop.ontohub.org