Break AppEngine support out of the core.

Add support for iterable headers.

Use new central artifact redirect link.

(cherry picked from commit dbf91444)

(cherry picked from commit 298454e0)

Conflicts:
	pom.xml

Fix usage of deprecated MimeUtil functions

Signed-off-by: NEddie Ringle <eddie@eringle.net>

Remove incorrect documentation for parseResponseType()

(cherry picked from commit cb322379)

Avoid an NPE when logging a null request arg

Switch to io.reactivex version of rxjava

This isn't the final resting place, but non-standard integrations like this are not going to live in the core.

Remove profiler.

This will be replaced by a generalized interceptor system.

Remove endpoint names.

Remove ResponseCallback.

Remove Client provider indirection.

Remove deprecated error identifier.

Those who desire lazy initialization can do so through a custom Client implementation which creates the delegate on first invocation. Also we can ensure OkHttp does initialization requiring i/o (e.g., disk cache) lazily.

Callback will be replaced with Call.

This isn't the right granularity of data about an endpoint and we never exposed this anywhere in the actual library.

This whole class is probably going to die or morph, but killing off tech debt before major refactorings makes me feel good.

Remove deprecated explicit encoded annotations.