rework help messages for fee-related options

- mention the units and show the default for -paytxfee
Merge pull request #4325

4aaa017 rework help messages for fee-related options (Philip Kaufmann)
qt: Log messages with type>QtDebugMsg as non-debug

More important messages should end up in the log no matter
if -debug=qt is set.
qt: Change serious messages from qDebug to qWarning

By changing the logging stream for warnings from qDebug to qWarning,
these will always be logged to debug.log.
Merge pull request #4448 from laanwj/2014_07_qt_payment_rq_logging

qt: Always log warning/error messages to debug.log
Clean up release-process.md after OS X gitian changes

This is PR #4271, but with the changes to the descriptors, both the names of the
files and the names of the intermediate build artifact archives, removed.
This also closes #3775 if it goes in, because it covers the changes in
that PR.
Fix the Qt5 build after d95ba75

Sorry, my own fault this time.
Merge pull request #4449

462ad22 Clean up release-process.md after OS X gitian changes (Micha)