Resolve context path issue when deploying to servlet container

[awoods]

Prior to this update, when deploying to a servlet container:

• the style.css does not resolve
• the favicon.ico does not resolve
• the "Linked Data Fragments" image does not resolve
• the contexts of datasource do not resolve

Supersedes: https://github.com/LinkedDataFragments/Server.Java/pull/52

[mielvds]

I ported the tests from #52 to this PR in https://github.com/LinkedDataFragments/Server.Java/tree/awoods-issue-52.

The tests fail on the baseURL. Could you have a look @awoods and align? Modify where you see fit of course.