Add parsing of Snapshot Dependencies list when fetching a build type.
ThrowIfHttpError method to be called in all request-posting helpers (previously, they would usually ignore errors).
Added missing REST error checks to Delete, Post and Put methods.
The former behavior would conceal the errors by silently ignoring failures, which looked innocent for methods like DELETE which expect no data in return.
Also, for raw methods (like PostRawAgentRequirement) where user has to guess the format, it's crucial to know the outcome.
Fix parameters mixup by enforcing API uniformity: data parameter goes before URI.
Used to be mixed up in the class, e.g. different overloads of Post had conflicting order.
As a result, there were calls (e.g. generic Post calling into nongeneric Post) mixing them up: using data instead of URI and URI part as data.
Pulling content-type and accept parameters up the call chain, to allow specifying them explicitly wherever needed.
Example for content-type: creating a new build-type requires submitting a plaintext name, but the content-type was hardcoded as XML; setting to text/plain made it work.
Example for accept: creating a new build-type yielded XML content by default, while we expect JSON for parsing, setting accept to JSON fixes the matter.
Adding one method to use locator for getting a build type, plus a few semantic methods which were missing from the implementation.
Merge pull request #36 from hypersw/master

Critical fixes, errors handling, and a few new API calls.