and make various internals of the class privatey

(This is not an ABI change, as package
com.sun.star.lib.uno.environments.remote is not considered part of the
stable URE interface; it is not included in the documentation at
<http://api.libreoffice.org/docs/java/ref/index.html>.)

Change-Id: I25719239c0208b770ecd96b452b4220ac02b309d
Reviewed-on: https://gerrit.libreoffice.org/25779Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>