Epsilon: pass prebid server version

[johnwier]

🔧 Type of changes

• new bid adapter
• [ X ] bid adapter update
• new feature
• new analytics adapter
• new module
• module update
• bugfix
• documentation
• configuration
• dependency update
• tech debt (test coverage, refactorings, etc.)

✨ What's the context?

Pass the server version number and a different displaymanager entry for better tracking on the backend

🧠 Rationale behind the change

It lets us differentiate between pbs and pbs-java, and the server's version number of the build is more useful to know what clients are using

🔎 New Bid Adapter Checklist

• verify email contact works
• NO fully dynamic hostnames
• geographic host parameters are NOT required
• direct use of HTTP is prohibited - implement an existing Bidder interface that will do all the job
• if the ORTB is just forwarded to the endpoint, use the generic adapter - define the new adapter as the alias of the generic adapter
• cover an adapter configuration with an integration test

🧪 Test plan

How do you know the changes are safe to ship to production?

🏎 Quality check

• Are your changes following our code style guidelines?
• Are there any breaking changes in your code?
• Does your test coverage exceed 90%?
• Are there any erroneous console logs, debuggers or leftover code in your changes?

[CTMBNara]

Remove VERSION_UNDEFINED and use VersionInfo.UNDEFINED (make it public).