Add presets to asset container settings

[ajcsilva]

This PR adds the ability to save image presets in the Asset Container settings.

[what-the-diff[bot]]

• Added sourcePreset and warmPresets to the AssetContainer class.
• Updated fillFromModel() method in AssetContainer class to include new settings from model object passed as parameter.
• Updated toModel() method in AssetContainer class so that it includes all of the current container's properties when creating a Model instance for saving into database table 'asset_containers'. This is done by calling $this->sourcePreset(), etc., which will return null if not set, or whatever value was previously assigned via ->setSourcePreset().