* Changed behavior of `readJournalFiles` to be identical to `readJournalFile` for singleton lists
* Balance Assertions have to be simple Amounts
* Add 'isAssignment' and 'assignmentPostings' to Hledger.Data.Posting and Transaction
* Implemented 'balanceTransactionUpdate', a more general version of 'balanceTransaction' that takes an update function
* Fixed test cases.
* Implemented balance assignment ("resetting a balance")
* Add assertions to show function
* updated the comments
* numbering is not needed in journalCheckBalanceAssertions
* remove prices before balance checks
* rename functions
When multiple files are specified with multiple -f options, we now
parse each one individually, rather than just concatenating them, so
they can have different formats.
Directives (like default year or account aliases) no longer carry over
from one file to the next. Limitation or feature ?
Using "hledgerdev" was a hack to help ensure that tests used a fresh
developer build by default. Now they specify "hledger" again, which fits
better with stack. It's up to the tester to make sure the desired
executable is first in PATH or specified with -w. (Note a couple of
tests currently don't obey -w and will always run "hledger", see addons.test).
