Feature request: Enhance netmail CRASH sending capability

Presently there are two ways to send a CRASH netmail to a destination:

1. Add a specific route to a destination via SCFG which uses CRASH and overrides any default routing (e.g. via a HUB).
2. Add "CR:" to the beginning of the subject line.

Proposed enhancement:

1. If a sender of a netmail has the necessary privileges to send CRASH netmail, prompt if CRASH is required as part of constructing a netmail. e.g. "Would you like to mark this netmail as CRASH? (y/n)"

2. If a recipient receives a CRASH netmail, and chooses to reply and that BBS user has CRASH privileges, then prompt the user if they want to use CRASH netmail, instead of having to add "CR:" to the beginning of each subject line in their reply. A similar prompt to the suggestion above could be used.

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