run fixOnRef and checkProjectSummations in all rem-mag iterations

[orichters]

Purpose of this PR

• run fixOnRef and checkProjectSummations in all rem-mag iterations
• they only take a couple of seconds, but it is good to know early whether the cascade has such problems
• also make sure make test-coupled-slurm checks whether dependencies are satisfied instead of failing in slurm
• also increase gdx dependency here (coming from remind2) to avoid fails

Type of change

• [x] New feature (well, a very minor one)

Checklist:

• [x] I performed a self-review of my own code
• [x] I explained my changes within the PR, particularly in hard-to-understand areas (really hard to understand!!!)
• [x] All automated model tests pass (FAIL 0 in the output of make test-coupled-slurm)