Add flags to skip warnings for new/delete/regen commands

[orndorffgrant]

Currently, devca asks for confirmation before continuing in three cases:

1. During the new command if the specified name already exists.
2. Always during the delete command.
3. Always during the regen command.

It'd be nice if there was a convenient flag to skip the warning for a user who knows what they're doing.

Our CLI should aim to be internally consistent, so the flag should be the same in all three cases, probably -f/--force.