Prevents crash on WPImageOptimizer

Adds a few extra checks to make sure we don't release NULL objects or
return invalid data.

Fixes #2713
Prevent crash on MediaService createMediaWithAsset

Uses existingObjectWithID instead of objectID, and checks that there's
an actual post to attach the media too.

If there is no post, `completion` will be called with a `nil` media
object.

Fixes #2719
Integrates the latest editor pod. Fixes an important regression.
Merge pull request #2720 from wordpress-mobile/issue/2719-fix-mediaservice-crash

Prevent crash on MediaService createMediaWithAsset
Merge pull request #2721 from wordpress-mobile/editor-integrate-latest

Integrates the latest editor pod. Fixes an important regression.
Updated media uploading alert text.
When uploading media, users are no longer...

...allowed to leave the post until the media upload is complete.
Make WordPressAPI pod point to a proper tag.
Merge branch 'release/4.6' of github.com:wordpress-mobile/WordPress-iOS into issue/editor-344-media-upload-blocker

# By Sérgio Estêvão
# Via Sérgio Estêvão
* 'release/4.6' of github.com:wordpress-mobile/WordPress-iOS:
  Make WordPressAPI pod point to a proper tag.
Updated to the most current 0.2.3 editor which contains a bugfix for image replacement
Merge pull request #2725 from wordpress-mobile/issue/editor-344-media-upload-blocker

Issue/editor 344 media upload blocker
No need to preserve offset when loading more.
Integrates the latest editor pod.
Adjusts appearance hierarchy for search bar's textfield.
Merge pull request #2729 from wordpress-mobile/editor-integrate-latest

Integrates the latest editor pod.
Updated provision profiles
Fixed privacy warning for location key
Rolls back 2612 due to issues related to kerning.
Merge pull request #2733 from wordpress-mobile/issues/rollback-2612

Rolls back 2612 due to issues related to kerning.
Makes appearance hierarchy more specific.