Change to/fromAscii to to/fromLatin1 for Qt5
Close connection on response->end()

Based on a patch by Sebastian Wallat:
https://github.com/swallat/qhttpserver/commit/196bcf1e9b6c8c39789ae364f678f377e7fbe072
Let the server act as a QML plugin

In addition to adding the necessary boilerplate, we also add a new
version of QHttpServer::listen(), in which the address can be given as a
string.  This can be used from QML, which doesn't have any equivalent
for QHostAddress.
Add example of a QML HTTP server