Add support script to generate the man pages from alr help

[stcarrez]

Man pages are generated by running the bin/alr help and formatting the output in troff and man macros. There is one man page for every alr command and alire command man pages are prefixed with 'alr-' (ie, similar to git man pages). The main alr man page is generated from the doc/introduction.md as well as some internal alr help (alr help aliases, alr help identifiers, alr help toolchains).

Man pages are generated in doc/man1 and this allows to setup the MANPATH environment variable to point to doc and easily look at the generated man pages. The following man pages are generated:

alr.1 alr-clean.1 alr-edit.1 alr-get.1 alr-pin.1 alr-run.1 alr-test.1 alr-version.1 alr-show.1 alr-update.1 alr-action.1 alr-config.1 alr-env.1 alr-index.1 alr-printenv.1 alr-search.1 alr-toolchain.1 alr-with.1 alr-init.1 alr-publish.1 alr-build.1 alr-dev.1 alr-exec.1

[Fabien-Chouteau]

As I said in the other PR, this should probably be generated by CLIC directly. See my proof of concept: https://github.com/alire-project/clic/pull/12

[stcarrez]

As I said in the other PR, this should probably be generated by CLIC directly. See my proof of concept: alire-project/clic#12

Ok. I'm not convinced this is the good way to have man pages. There are many documentation that you cannot put in the code and that is desirable for a man page. I agree that this python script is a hack but well, now I have my man pages.

Anyway, I'll keep that python script and move it to my debian support files. No need to keep this pull request then.