Merge pull request #49 from nemomobile/vdv-devel

[nemo-qml-plugin-email] Turn messagesCount into a property.
[nemo-qml-email-message] Download html/plain message body when is not yet available.
Merge pull request #50 from nemomobile/email-decoding

[nemo-qml-email-message] Download html/plain message body when is not yet available
[nemo-qml-plugin-email] Don't emit htmlBodyChange for messages wihtout html body.