add bc

[nasbdh9]

Following are request thread from community:

Problem/Justification: bc is included in core and is required to do more complex math in scripts such as TrueNAS-Report.

Impact: Minimal impact For those that do not need a command line based calculator

User Story: I envision users being able to use scripts like TrueNAS-Report that require complex math without requiring the user to install additional software in the base system.

[1] https://forums.truenas.com/t/include-bc-in-scale/8933