NEW Refactor to not require sake

[chillu]

There's no straightforward way to have sake run without a database connection.
When using a "fake" HTTPApplication for CLI execution, it executes middleware which rightfully assumes a database connection (e.g. fluent is getting available languages to modify routing).

Todo:

• Remove error handlers assuming HTTP context (e.g. SERVER_PROTOCOL)
• Test with composer v1
• Test clean 4.x install
• Test that it creates files in public/assets
• Fix reliance of error handling on $_SERVER

Relies on silverstripe/silverstripe-framework#9977

Related:

• RFC: Avoid HTTPApplication for CLI
• RFC: Use Symfony Console for better CLI output

[chillu]

Next frontier on this is error handling which relies on $_SERVER environment variables that don't exist outside of a HTTP context, and are currently mocked on CLI execution through HTTPRequestBuilder::createFromEnvironment().