Remove dead code and unused imports
Merge pull request #106 from bpollack/deadcode

Remove a lot of dead code and unused imports
Do not get into a 500 state when a bad app registers

Previously, the DataCenterInfo was not effectively "validated" until read time,
which meant that a malicious (or simply badly coded) app could take the Eureka
cluster offline by specifying a dataCenterName that wasn't one of Amazon,
MyOwn, or Netflix.  Move the validation code to write time by doing the
conversion to DataCenterInfo.Name as part of the deserialization process.