Qt Creator has no concept of device specific deployment paths

Currently we place the following snippet in every application .pro file in order to make Qt Creator aware of the path it should deploy the application to on various devices:

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

This is less than ideal because the default deployment root is a device property and should be available to other project managers, too. Also, this is incomplete as it only handles qnx and non-android unix systems.

In the discussion about QTCREATORBUG-21225 we discovered that we have to do practically the same thing for qmlproject files, and eventually it will probably come up for cmake, qbs, etc.

Qt Creator should know device specific default deployment roots and it should be able to create project specific deployment paths from those. The entries in the project files should still be possible, but optional.