BackendManager: Cache backend environments to avoid unnecessary requests
Rename internal helper functions to match server terminology.
Fix camel case in EnginioClient: setserviceUrl -> setServiceUrl
Add a bit of docs.
Add backend manager function to query backend environments
and combine it with the local environments cache.
Add backend manager function to get backend API keys
e.g. {"backendId" : "ID", "backendSecret" : "SECRET"}
Improve image-gallery example.

AnimatedImage with gif crashes on some machines.
Cleanup layouting and other aspects.
Merge pull request #124 from gladhorn/imagegallery

Improve image-gallery example.
Make the search test use it's own backend.
This is the first step of a migration to per-testcase backends.
Merge pull request #125 from nierob/smallFixups

Fix potential memory leak in EnginioModel
Merge pull request #126 from bbandix/backendManager

Backend manager improvements
Merge pull request #121 from nierob/docs

Add a bit of docs.
Implement file download variants
Use thumbnails in the list

sec
Image Gallery example C++
Improve image-gallery example even more

Get the images from the right url, use
variants so that we have thumbnails in the list,
big images in detail view.
Merge pull request #106 from gladhorn/thumbnails

Thumbnails
Use common delete_icon.png for todo and image gallery examples