Introduce "named" journals

[refactorsaurusrex]

Currently, the application assumes a single "default" journal. You can also have additional, non-default journals - which basically just amount to an independent collection of journal files - but the application doesn't support that particularly well. Instead, separate journals should be nameable and all cmdlets should be given a -JournalName parameter to indicate which journal to target. However, there should still be one "default" journal so that -JournalName isn't required for every operation.

Collateral Damage

• Should compiled entry functionality also be updated to pull entries from any number of named journals?