Glide process image assets on upload

[jesseleite]

Closes statamic/ideas#485
Closes statamic/ideas#804
References statamic/ideas#300

• Add new glide config to asset container edit form.
  
  • Wire up new glide_source_preset config.
    • Glide process images on upload.
    • Fix error when uploading non-glideable filetypes.
    • Hook up mark watermarking.
    • Add test coverage.
  • Wire up new glide_warm_presets config.
    • Ensure user can save glide_warm_presets: false to disable intelligent warming.
    • Glide configured warm presets on upload.
    • Glide intelligently on upload when warm presets are not configured (everything except glide_source_preset).
    • Glide configured warm presets when running pls glide:generate-presets.
    • Add test coverage.
  • Add new translatable strings to translation files.
  • Documentation PR.
    • Document new Glide processing Asset Container config docs#869

[what-the-diff]

• Added source_preset and warm_presets to asset container config.
• Updated the uploader component in CP to use these new settings, if present on a given container.
• Refactored some of the file uploading logic into an AssetUploader class that can be used by other parts of Statamic (e.g., File Upload fieldtype). This is similar to how we have FieldsetBlueprintLoader for blueprints, but it's not quite as generic because there are still some assumptions about where files will end up being uploaded from/to based on whether or not they're assets vs just regular files being uploaded via a form submission somewhere else in Statamic (like with forms addon). I'm open to suggestions here! :)
• Added source_preset and warm_presets to asset container config
• Updated the AssetContainersController with new fields for these settings
• Updated GlideManager::server() method to accept an array of overrides, so we can pass in a custom cache path when processing images from assets that have their own preset defined (ie: not using the default)
• Added a few new config options to AssetContainer
• Updated the asset upload process to use those configs if they're set
• Created tests for all of that stuff, including some Glide integration testing (which is why I added define-env)