Add pk;a/Account as an alias/alt for System for pk;system commands

Reasonings:

• People ask if they can register a 2nd System to PK & it has to be explained that they need to 1) Think of their PK “System” as their PK “Account” and 2) use Groups to mimic/create sub/multi-system functionality. Having Account as an alias would potentially help with this?
• Not everyone is comfortable having to use the term “system” for themself bc that’s the one term PK uses, and they’d be more comfortable with something more neutral/generic like “account”