Bugfixes and larger AppIcon

[relikd]

Hi there and thank you for this QL plugin.
My commits follow semantic naming so it is probably easier to read by commits than by overall changes ;-)

This PR:

• fix codesign on 10.15 has no --xml flag. f5facd5
• fix crash if Plist key is not present. 2a339fc (in my case CFBundleShortVersionString for an iOS 3.2 ipa)
• use higher resolution app icon (iTunesArtwork) if available. 5ddcdc9
• slightly larger icon in preview (and fixed-width icons for consistent placement).
• some refactoring to reduce duplicate code

PS: I removed the @"-x", @"*/*/*/*" args as I think it is not used for single file unzips anyway? Let me know if this was a mistake. Otherwise the console will always printing the following error:

caution: excluded filename not matched:  */*/*/*

[relikd]

• fix IconFlavor

And one suggestion:
I think we should remove the .provision drawing in the thumbnail generator. Isnt the thumbnail icon cached anyway? How useful is an expiration status if it is not updated?

[ealeksandrov]

Great work, thanks for the PR!
I'll take closer look and test it later this week.

[relikd]

I also did a complete refactoring of the code to have a more modular structure. https://github.com/relikd/ProvisionQL/tree/refactor_rewrite
Not sure if you first want to review the changes in this PR or jump into the refactor straight ahead (I can create the necessary PR if you like).

In the next few days I plan to:

• implement Want to show Apple ID info #26
• try to use zlib to unzip ipa content instead of launching a sys command
• maybe get support for Asset.car files if I get the private API to work. (or fallback to convert with iconutil)

[ealeksandrov]

Looks great, thanks!
I've noticed indentation inconsistency and converted all tabs to spaces before merging.