Modify blob upload API

- Ensures new uploads and resumed upload statuses always return an offset of 0. This allows future clients which support resumable upload to not attempt resumable upload on this version which does not support it.
- Add PATCH support for streaming data on upload.
- Add messaging to specification that PATCH with content range is currently not supported.
- Update PUT blob to only support full data or no data, no more last chunk messaging as it was not supported.

closes #470

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

docs/spec/implementations.md

@@ -0,0 +1,26 @@
+# Distribution API Implementations
+
+This is a list of known implementations of the Distribution API spec.
+
+## [Docker Distribution Registry](https://github.com/docker/distribution)
+
+Docker distribution is the reference implementation of the distribution API
+specification. It aims to fully implement the entire specification.
+
+### Releases
+#### 2.0.1 (_in development_)
+Implements API 2.0.1
+
+_Known Issues_
+ - No resumable push support
+ - Content ranges ignored
+ - Blob upload status will always return a starting range of 0
+
+#### 2.0.0
+Implements API 2.0.0
+
+_Known Issues_
+ - No resumable push support
+ - No PATCH implementation for blob upload
+ - Content ranges ignored
+