Add support for CB7 and CBA file format

[Nguyen Duc Minh]

Add support for CB7 (7-Zip file format specialized for ebooks) and CBA (ACE file format specialized for ebooks).

Having these added will definitely be a good quality of life update for not-so-experienced users.

[Kovid Goyal (kovid)]

CB7 I could possibly look into if the python builtin lzma module handles
it. CBA is not worth the effort. Please attacha sample cb7 document or
two for me to work with.

 status incomplete

[Nguyen Duc Minh (minhngoc25a)]

I don't know any existing program that creates .cb7 file directly, so I created this archive using 7-Zip and renamed the extension.

[Kovid Goyal (kovid)]

if there arent any programs that create cb7 files, why would calibre
need to support them? where are they coming from?

[Nguyen Duc Minh (minhngoc25a)]

Because it's one of the Comic book archive (https://en.wikipedia.org/wiki/Comic_book_archive) file format? I think Calibre should support all of those formats for a better experience, but feel free to close this bug if you disagree.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased