Onboarding: installing system tools requires sudo

In 2.1.0b the commands to install the Artifact tools are:

    wget https://d1b0l86ne08fsf.cloudfront.net/mender-artifact/3.1.0b1/linux/mender-artifact
    chmod +x mender-artifact
    wget https://raw.githubusercontent.com/mendersoftware/mender/2.1.0b1/support/modules-artifact-gen/single-file-artifact-gen
    chmod +x single-file-artifact-gen
    mv mender-artifact single-file-artifact-gen /usr/local/bin/

The last command (mv ...) will fail due to lack of administrative permissions.

master seems to have this fixed already, but it needs to be backported to 2.1.x before the final 2.1.0.

A few related suggestions:

• Make it more clear that these commands should be run on the workstation, not the device. This is stated at the top with a quite grey font, but I think there's a high risk the user will run them on the device because he previously copied commands to the device to install Mender.
• Can we have Mac support for these tools too (e.g. tab for Linux and Mac)?