Adding flags: -y and -q

[velle]

If I make a PR for this, will you consider it? I will try to place the code in a central place, so it will affect all commands.

I suggest the behavior below, which I believe follows conventions.

Default (no flags):

$ gc2 schema drop testschema
✔ ⚠️ The whole schema will be deleted. Are you sure (y/N) y
Schema testschema dropped.
$

No confirmation prompts:

$ gc2 schema drop -y testschema
Schema testschema dropped.
$

Quiet (also means no confirmation prompts):

$ gc2 schema drop -q testschema
$

$ gc2 schema drop -q no_such_schema
⚠️ Schema not found
$