compliance: be compliant with dist-spec compliance tests

dist-spec compliance tests are now becoming a part of dist-spec repo
itself - we want to be compliant

pkg/api/regex.go:
	* revert uppercasing in repository names

pkg/api/routes.go:
	* ListTags() should support the URL params 'n' and 'last'
	  for pagination

	* s/uuid/session_id/g to use the dist-spec's naming

	* Fix off-by-one error in GetBlobUpload()'s http response "Range" header

	* DeleteManifest() success status code is 202

	* Fix PatchBlobUpload() to account for "streamed" use case
	  where neither "Content-Length" nor "Content-Range" headers are set

pkg/storage/storage.go:
	* Add a "streamed" version of PutBlobChunk() called PutBlobChunkStreamed()

pkg/compliance/v1_0_0/check.go:
	* fix unit tests to account for changed response status codes

pkg/api/regexp.go

@@ -6,7 +6,7 @@ import "regexp"
 var (
 	// alphaNumericRegexp defines the alpha numeric atom, typically a
 	// component of names. This only allows lower case characters and digits.
-	alphaNumericRegexp = match(`[a-zA-Z0-9]+`)
+	alphaNumericRegexp = match(`[a-z0-9]+`)
 
 	// separatorRegexp defines the separators allowed to be embedded in name
 	// components. This allow one period, one or two underscore and multiple