Further changes to the MonkeyTester application:

- remember split pane divider ✔
- use 'private' instead of 'protected' ✔
- added more scripts to the 'writing systems' text sample ✔
- added RTL window control menu ✔
- added embedded swing/fx in tools ✔
- added copy popup menu in clipboard viewer ✔
- added the custom css field to the css playground tool ✔
- added many new pages ✔
- split XYChartPage into separate pages ✔
- switched to use property sheets (some choices might be incomplete) ✔

To be continued, JDK-8328828