Load thumbnail instead of lowest resolution

Lowest resolution retrieval then scaling is too expensive for
very large image. Load the existing thumbnail instead.
Remove commented out code.
Retry when a lock exception occurred. (see #10604)

When running the server locally and using 4 re.
lock exceptions can occur while rendering an image, retry.
Fix max retry to 2.
Do not reactivate RE when reconnecting if not active.
No longer handle null result.

This is no longer required, the image is now updated
using the update method.
Remove commented out code.
Remove method w/o implementation.
Review shut down sequence (see #10633)
Fix left shift (see #10595)
Remove import (eclipse import completion)
Remove System.err commented out.
Fix square selection
Remove commented out code.
Merge pull request #987 from jburel/rebased/develop/big-image-3

Big image 3 (rebased onto develop)