Clean up license names + add more licenses and disambiguations

[gardenappl]

(This is built on your latest commit but I'm not sure if I should open this PR here or on the upstream repo)

This PR introduces better handling of license name variants via the clean_license_name function. It takes a license name and:

• removes the "custom:" prefix
• turns it into lowercase
• removes whitespace, commas, quotes, dashes and underscores

This means that, for example, "cc-by-sa 3.0" and "custom:CCBYSA3.0" are treated as the same license. The --list-licenses option prints the most popular variant.

I've also spent some time adding more licenses and packages into the "unambiguous" db.

• AFL-3.0 - Academic Free License, recognized by FSF as free but not GPL compatible
• Beerware - very permissive "joke" license
• BSL - approved by OSI, same as "Boost" from what I understand
• EDL - used by Eclipse's jaxb-ri, it's basically just BSD-3
• ImageMagick - not recognized by OSI or FSF but Debian allows it
• Unicode-DFS - recognized by OSI and FSF in various forms
• UCD - used by xorg-font-util, not recognized by OSI or FSF but Debian allows it
• WTF - same as WTFPL
• unambiguous_db now contains a bunch of xorg/x11 packages (all of which use some variant MIT/X11), some Mesa packages, some non-free packages, and some others like youtube-dl, zsh and zathura.

[psvenk]

Thank you for the pull request! Sorry for the late response; for some reason, I did not get a notification email from GitHub about this — maybe this is because the PR was opened on a fork.

In any case, this looks good to me, and I'm happy that you took the initiative to do this work, opened orospakr#24, and created the new AUR package. Thank you again; I hope that our changes get upstreamed.