Make every request timeout in 30 seconds.

Created TimeoutFilter to intercept all incoming requests and timeout if a
request is not completed in 30 seconds. The timeout duration is fixed to 30
seconds for now, but it needs to be configurable.
Add admin page header.

Currently, there is only Home tab.
Show the server information in admim home page.

The server information includes:
- Play mode
- PlayVersion current
- PlayVersion sbtVersion
- PlayVersion scalaVersion

More will be added later.