method to remove/reset/reload routes

[vasiliy-t]

Would be nice to have a method to remove or reset already registered routes as part of public http API. Possible scenarios of application:

1. handlers reload for e.g. in case of application code upgrade
2. live coding for e.g. i'm working on application that accepts webhooks and to iterate fast I setup webhook and traffic tunneling via ngrok to my localhost, then I start tarantool with httpd server and write and debug handler in live mode - write code, trigger webhook, write next version, trigger webhook etc.
3. different maintenance scenarios e.g. degrading an API to allow only reads and disabling all write methods

[Totktonada]

Cartridge hacks it. I would also note this fixup for the routes deletion code.

[Totktonada]

See also #110.