Initial pkpass support

[TheLastProject]

This will probably take a bit longer to make completely useful, but this at least does the initial parsing. Marking this WIP just because I believe in sharing progress to allow for early feedback.

When this is done, it will fix #309.

TODO:

• [x] Parses https://github.com/keefmoon/Passbook-Example-Code/blob/master/Pass-Example-Generic/Pass-Example-Generic.pkpass successfully
• [x] Unit tests
• [x] Make unit tests directly work with pkpass files (for more easy extending in the future)
• [X] Parsing relevant extra fields
• [x] i18n support
• [ ] Open .pkpass files from browser

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This change is 

[TheLastProject]

Documentation: https://developer.apple.com/library/archive/documentation/UserExperience/Reference/PassKit_Bundle/Chapters/TopLevel.html#//apple_ref/doc/uid/TP40012026-CH2-SW1

[TheLastProject]

I've opted for using a new EXTRAS database field to store this all in, because putting all of this data in the note doesn't seem doable. See https://github.com/brarcher/loyalty-card-locker/issues/309#issuecomment-565748328 for how this looks to the end-user.

[TheLastProject]

i18n is working, but I need to fix all the tests still:

[TheLastProject]

While not perfect, it does enough to be useable. I guess I consider this to be "ready for review" now, @brarcher.

It's a rather huge change, so to explain the architecture a bit:

• There's a new ExtrasHelper which stores "extra" data. The reason for this is that (1) note doesn't support i18n, (2) there's simply way too much data to store in a note and still have a decent user experience
• The ExtrasHelper saves to the database as JSON and parses the JSON from the database. This is on purpose because (1) to my knowledge JSON by itself does not have code execution exploit risks like other ways of storing data does, (2) it makes it easy to share it with the existing share feature and (3) there are no real guarantees as to what fields there will be which makes it difficult to create a good DB structure for

Some notes:

• I'm honestly not happy with the whole codebase being filled with throws JSONException now, but I'm not sure how else to make this work...
• Android intents are very confusing but this at least consistently works for downloaded .pkpass files in a file manager.
• We lack a proper i18n chain. Right now it's just user's preferred language -> en -> untranslated. This means that if Android returns es_AR for example, we'll likely fail to return the es translation and will instead return the en one. I do not yet know how to properly fix this.

[TheLastProject]

I couldn't resist and I'm sure the legal worries of #303 don't apply when they literally put the icon in the file that's provided.

[airon90]

I suppose that the name of the app should be changed, as boarding cards or event tickets are not loyalty cards. I am going to open a new issue about that.

[TheLastProject]

I personally would keep the app name the same and just write in the description it also supports event tickets and stuff.