Build and distribute CLI for Linux and macOS

[cschwan]

We currently build the CLI when making a release, but there are a few items to be done:

• write a install-cli.sh similar to our install-cli.sh installation script; implemented in commit 29fd440
• document install-cli.sh
• build and ship also manpages
• macOS has --features=applgrid,fastnlo currently not enabled, and therefore importing APPLgrids and fastNLO tables will not work on macOS fixed in Fix building the CLI on macOS #269
• on Linux (and for macOS) APPLgrids cannot be imported in the .root format, for which we'd need to install ROOT in the container. Furthermore, we'd need to link everything statically, which I'm not sure is possible

[cschwan]

We now have a first candidate of the CLI built for v0.7.4, however the static linking doesn't work properly on Linux. To fix this, we should try to link to LHAPDF only in managed-lhapdf and not in pineappl_applgrid. We're also linking to LHAPDF in pineappl_fastnlo, but there it's probably unavoidable.