Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Add cluster server list and assign page and client list page (for a specific app)

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Fixes #231: when resource name is too long in resource page, the name will jump out and cover other layout
- Hide `origin` input view in degrade rule dialog
- Refine style and color of buttons in dialogs
- Add support for exception count in degrade rule
- Other improvements

Signed-off-by: Eric Zhao <sczyh16@gmail.com>