Warn when DayOne/directory journals have encrypt: true in config

[micahellison]

Relates to #1243 and is built off of #1315.

Right now jrnl is silently accepting the "encrypt: true" config values for directory and DayOne journals, even though it's not encrypting them. This warns the user about it.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have tested this code locally.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.
• All tests pass.

[wren]

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