Use take instead of value and remove
Chunked upload
Use a QIODevice instead of buffering in QByteArray when uploading
Make file test independent.
Fix chunked upload chunk-size and test

The position of the QIODevice turns out to not work,
when it's read, sometimes the position advances too far.
This is only the case on tiny chunk-sizes,
as is the case in the test.

The test sets a small chunk size which means the image will
be uploaded in 8 parts.
Merge pull request #82 from gladhorn/chunked_upload

Chunked upload
Remove an unused function

The function is a leftover before API cleanup.
Fix a possible invalid read and write.

It is possible that authentication request survived EnginioClient
destruction. In such case finished signal triggering
SessionSetterFunctor was causing an invalid read and write to already
deleted EnginioClientPrivate.
Introduce authenticationState property in EnginioClient.

During API we agreed that isAuthenticated bool is not good enough, for
example it is not trivial to have a spinning icon during login phase,
without tracking right signals.

The enum structure is not final yet and I'm sure we should have another
round of review for it.
Emit sessionAuthenticated together with EnginioReply

The signal is replacement for removed identityToken.
New tests for identity check

Setting identity should reset the sessionToken, which is part of a
QNetworkRequest header.
Reuse a QStringLiteral