Utility scripts I use in accounting for shared expenses for projects or trips.


match_expenses is working and should be moved to the main codebase. Here's what
I need to do to it:

- Move the SQL shell syntax to v2, whereby a "FROM <filename>" clause is
  implemented to select an arbitrary subset of transactions.

- A function to easily invoke this selector on a list of entries should be
  provided.

- match_expenses should be renamed join_transactions.

- It should be modified to accept two FROM... WHERE... clauses as in the above,
  and these should be how the user provides two subsets of transactions to be
  paired up together.

- Tests should be added for it.

- It should be moved under beancount/scripts.
