IDEX-1664: disable some actions in RO mode

Also the next pull requests should be merged:
- https://github.com/codenvy/plugin-datasource/pull/222;
- https://github.com/codenvy/plugin-hosted/pull/84;
- https://github.com/codenvy/plugin-java/pull/45;
- https://github.com/codenvy/plugin-sdk/pull/9.