[ENHANCEMENT] provide a command line interface to the rcorder strings

[SchaichAlonso]

Is your feature request related to a problem? Please describe.
#629 has introduced rcorder(8) jail startup ordering support.

While something like

sed -i bak $'1i\\\n# PROVIDE: db\n' /usr/local/bastille/jails/db/jail.conf
sed -i bak $'1i\\\n# REQUIRE: db\n' /usr/local/bastille/jails/alfa/jail.conf

can be used to "enable" alfa's dependency on db in the example of #629 in a somewhat automated way , the /usr/local/bastille/jails/ prefix of the jail config file name passed to sed(1) is a deployment-specific setting tunable in bastille's config file.

Describe the solution you'd like
The bastille command line utility should have the ability to modify the jail.conf files and add/remove/printout the rcorder contraints of it's jails. For jails with multiple rcorder constraints, it should be able to remove the constraints individually, e.g.

# REQUIRE: db named
# REQUIRE: nginx
# PROVIDE: dyndns
dyndnsjail {
... 

after imaginary bastille rcorder dyndns remove require db should leave

# REQUIRE: named
# REQUIRE: nginx
# PROVIDE: dyndns
dyndnsjail {
...

Describe alternatives you've considered
Manually editing the jail configs... which is prone to mistakes.

Additional context
Eventually, the destruction of jails that have other jails depending on them should emit a diagnostic, as should the attempt to add a require statement that has no jail provide-ing it (yet).

[tschettervictor]

I'm wondering whether it would be better to use "priority" as iocage does instead of the current rcorder implementation.

This could mean having an additional parameter but just thinking...