Create semantic interface for Constants

[cbreden]

This one may be a bit more abstract. It might be worth having a utility class that can help enumerate many of SoftLayer's constants. Operating system types (plus dynamic handling of the magic strings like *_LATEST), routing types, etc.

On a case-by-case basis, some of these will go into the other objects. But there might be a few stragglers that have no clear home.

[SLsthompson]

Edited the original message to remove references to "data centers" as those are addressed separately in issue #40

[SLsthompson]

Edited the original message to remove the reference to Ticket Subjects which were addressed separately as issue #41 and were resolved in the 2.0 version of the Gem.