Resolve "Reorganize `/etc` and `/share` folder"

Closes #137

See merge request !106

Add `compiled/share` to build artifacts

`scripts/runner.sh` now saves logs for the applications it tries to run and
prints them if they cannot be started.

Scripts for controlling ad-hoc storage services now reside in
`CMAKE_INSTALL_FULL_DATADIR/scord/adhoc_services.d`, typically
`/usr/share/scord/adhoc_services.d/`.

Resolve "Add Slurm CLI plugin"

Closes #134

See merge request !95

Rename CLI options

Also, move job registration into `scord` to `slurm_spank_user_init` so
that it works both in `srun` and `sbatch`/`salloc`.

- `plugins/slurm/scord_prolog.sh`: Prolog script. Starts `scord-ctl`
   server and sets up environment.
- `plugins/slurm/scord_epilog.sh`: Epilog script. Stops `scord-ctl`
   server and cleans up environment.
- `plugins/slurm/scord_common.sh`: Common code to prolog and epilog.

Merge branch 'amiranda/119-add-a-user-level-library-for-functionalities-not-requiring-direct-scord-intervention' into 'main'

Resolve "Add a user level library for functionalities not requiring direct `scord` intervention"

This MR adds the library `libscord-user.so` with user-level interfaces to request
data transfers from `scord` from application code.

Closes #119

See merge request !103

Resolve "Tests require `scord.conf` to exist in `/etc`"

Closes #145

See merge request !102