Improve budget filtering, allow "last-used" as an argument

[mbrajk]

Allows for filtering to all of the budgets found by the filter passed as the first argument on the command line. Previously the first found budget was automatically selected.

Additonally, last-used can be passed as the first argument on the command line to default to the last used budget, however it is a less than ideal experience due to the issues described in #9.

Draft until the following are included in this PR:

• ~need to hide last-used if --open flag is passed, feature was inadvertently removed~
• ~Display an error if last-used and --open are included on the command line together, this may be easier if last-used is changed to its own argument e.g. --last-used~

Fixes #24 Fixes #9 Fixes #28

[mbrajk]

Added error message when --last-used and --open are used together.

PR still on hold until I remove the ability to provide "last-used" as a search term as allowing the command --last-used is the preferred route.

[mbrajk]

Removed the ability to provide "last-used" as a filter. Preferred route is now to use --last-used as a flag.

Additionally, last used budget is now hidden from the budget list when --open flag is provided as we are unable to open it due to the structure of the YNAB API. Specifically getting the budget id takes a full budget download which takes an excessive amount of time.