pluginmanager: fix parsing of TYPELIB_PLUGIN_PATH

the last list-entry was skipped... not detected because the ruby-testsuite
does not test the plugin in the build-folder, but the one installed...

Signed-off-by: Martin Zenzes <martin.zenzes@dfki.de>
test/ruby/CMakeLists: make the environment proper for testing

now the testsuite will not test installed "RUBY_PLUGINS"... maybe add a
second test-invocation?

Signed-off-by: Martin Zenzes <martin.zenzes@dfki.de>
test/ruby/CMakeLists: add a second ruby-test running against the installed plugins

which is the same test as before this odyssey began

Signed-off-by: Martin Zenzes <martin.zenzes@dfki.de>