starthawaii: do not suppress qdbus error messages

With stdout suppressed, qdbus does not print anything to stderr in the
good case. And in the bad case, we do want to see the error output.
Flat style

Issue: #119
client: Add a switch to enable the QML debugger

Issue: #120
starthawaii: Pass the -d switch when QML debugging is requested

Issue: #120
Update README.md with debugging instructions

Issue: #120
client: Don't translate "Hawaii Shell"
client: Use QStringLiteral for application information
client: Specify a translation context for command line arguments

Using QObject::tr() result in a vague "QObject" context that will make
translators work harder.

Issue: #121
compositor: Specify a translation context for command line arguments

Using QObject::tr() result in a vague "QObject" context that will make
translators work harder.

Issue: #121
client: Enable translations

Issue: #121
compositor: Enable translations

Issue: #121