Bug 11230 - Refactor C4::Stats::UpdateStats and add UT

Bug 11230 - Refactor C4::Stats::UpdateStats and add UT

This patch
- refactors C4::Stats::UpdateStats (it now takes a hashref as unique parameter, instead of a list of parameters)
- add UT for it
- change the calls made to this sub in C4::Accounts and C4::Circulation

Additionnaly it also
- adds POD to C4::Stats::TotalPaid
- adds some comments to C4::Stats::TotalPaid (I think I found some errors in it)

To test :
1. run "prove t/db_dependant/Stats.t -v"
2. make some circulation operations (checkout, checkin, renew, localuse)
check the operations are rightly recorded in Statistics table (with a SQL query like "SELECT * FROM statistics WHERE datetime LIKE "2013-11-15%", if you run your test on the 15th november)
3. make some fine payments operations (writeoff, payment)
check the operations are rightly recorded in Statistics table (with a SQL query like "SELECT * FROM statistics WHERE datetime LIKE "2013-11-15%", if you run your test on the 15th november)

Note that there is probably an issue to fix in Accounts.pm : the user is saved instead of the branch. But this is not the purpose of this patch, so I kept the previous behavior for the moment.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work, test pass, isse/return/writeoff recorded on statistics
Removed a "=back" to make happy koha-qa
No other errors

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>