Install applications from pbw file

[matejdro]

Similarly to original Pebble app, new app should also be able to install pebble apps from pbw files.

Upon tapping on pwb file in any file browser app (or in browser's downloads list), Cobble app should open, displaying information about the app and offering user to install it.

Progress in https://github.com/pebble-dev/mobile-app/tree/pbw_install:

Stage 1:

• Native - Open and read PBW file metadata (Flutter has no appropriate zip library)
• Flutter - Display rudimentary install confirmation prompt
• Flutter Native - Copy file to the app storage

Stage 2:

• Flutter - Insert app into BlobDB
• Flutter - Open app on the watch
• Native - Send app data to the watch on request
• Flutter - Display installation progress
• Flutter - Add delete app button
• Both - Delete PBW file upon deleting app

Stage 3:

• Flutter - organize background code (split into multiple files)
• Flutter - Close install dialog when install is complete
• Flutter - Clear and reinstall all apps when watch is unfaithful
• Flutter - Fail gracefully if app does not support connected watch
• Flutter - Force reinstall when installing already installed pbw
• Flutter - Display message to the user if watch is not connected
• Flutter - display app compatibility
• Filter pbw intents to only content uris