Improve documentation re purpose of installing and using JIRA 4.0 Beta 1

After Summit we get a couple cases a day in SAC where users report problems re beta1.

The problems are related to:

• usage of the incompatible plugins,
• problems resulting from not following the upgrade documentation,

Moreover recently we've had a user who used the pre-release to upgrade his production JIRA .

Despite that we can't force people to the right thing, we can make it much more obvious what is the purpose of this release and how it should be used. Our customers aren't only tech people, but also users who 'click next, next and let see what happen' and those need more attention.

For e.g. we should:

1. Link to the upgrade page tailored to the beta release on the download page. The same as for 'normal' JIRA release.
2. Clearly state that this release is not supported through SAC and all issues agains it should be reported in JAC.
3. If we value feedback of less experienced users we should have a guide on what we want them to evaluate.
4. Have warning in red - Do not use it for production installation.
5. Have warning in red - Ensure that your plugins are suitable for the JIRA beta1

As the result of similar work on the Starter license we could benefit from lowering down number of support requests.