Merge lp://staging/~rafalcieslak256/ubuntu-accomplishments-viewer/982246 into lp://staging/ubuntu-accomplishments-viewer

This branch is meant to fix #982246 in the viewer, by introducing proper PATH setting.

This merge is related to https://code.launchpad.net/~rafalcieslak256/ubuntu-accomplishments-daemon/982246/+merge/102030, it fixes the same problem in the daemon.

The client-side fix turned out to be much simpler, as it is enough to repair the PATH in bin/accomplishment-viewer launcher. The problem was that the launcher was setting the path correctly only if it was installed to /opt/extras.ubuntu.com/accomplishments-viewer, I made it simply add the required locations based on PROJECT_ROOT_DIRECTORY.

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That change introduces one more great feature:
It is now possible to pair a certain version of daemon/client. By installing BOTH the daemon and client to the same directory one can be sure that the client will use the api files from exactly that daemon installation.

Also, although I have not checked it because I do not have these packaging scripts, I think it may be beneficial when it comes to packaging. I'm unsure of how it works with python, but e.g. autotools love to set their custom prefix for packages, and supporting that within the app's code is a desired feature.

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The next step would be to fix #982047 so that it works not only in packages, but in any installation :-)