eliminated old makedist_bundle and remote_dmg: build_release does everything in Scala; more robust components and classpath via Other_Isabelle; updated macos_app to include full dmg template; misc tuning and clarification;

tuned;

updated to jedit_build-20181203 (according to d70767e508d7);

Components.download similar to "isabelle components", but without unpacking;

clarified signature;

clarified signature;

more explicit support for Isabelle system components; activate_bundled_components: check component dir as in makedist_bundle;

more operations;

static type for Library.using: avoid Java 11 warnings on "Illegal reflective access"; more uses of "using";

tuned;