more robust: provide docking framework via base plugin; --HG-- rename : src/Tools/jEdit/src/dockable.scala => src/Tools/jEdit/src-base/dockable.scala rename : src/Tools/jEdit/src/pide_docking_framework.scala => src/Tools/jEdit/src-base/pide_docking_framework.scala
separate base plugin for important services that should be always available, despite startup errors of the main plugin; --HG-- rename : src/Tools/jEdit/src/isabelle_encoding.scala => src/Tools/jEdit/src-base/isabelle_encoding.scala