Use fake reply in EnginioModel::remove and EnginioModel::setProperty.

It unifies behavior between EnginioModel and EnginioClient
Add more QVERIFY in EnginioClient tests
Do not return null EnginioReply in EnginioModel::setProperty.

Create a proper reply when an user try to update unknown role.
Make test check only one thing

EnginioModel is allowed to make additional requests so the test should
query only requests that were created by it.
Move re-parenting of a QNetworkReply instance to the EnginioReply ctor.

EnginioReply should take ownership of QNetworkReply, so there is no need
for manual re-parenting.
Merge pull request #146 from nierob/smallFixes

Small fixes
Remove imvalid TODO comment
Merge pull request #147 from gladhorn/docs

Add a tutorials page to docs
Unify a bit look of qml and widget version of TODO examples
Merge pull request #149 from nierob/example

Unify a bit look of qml and widget version of TODO examples
Document the image gallery qml example.
WIP: C++ ToDo docs
Improve todo example docs
Remove BACKEND_API_URL from examples since it is internal API.
Improve C++ Todo example documentation
Merge pull request #151 from nierob/docs

Improve C++ Todo example documentation
Fileter out objects without image reference
Do not disable append button in Todo example
Merge pull request #152 from nierob/examples

Examples
Improve reply finished signal handling

Connecting finished signal to a component is a bit dangerous as the
component can be deleted at any point.