[FIX] hr_timesheet_sheet: allow writing attendance line not according to the...

[FIX] hr_timesheet_sheet: allow writing attendance line not according to the date order, and check that the attendances satisfy the alternance constraint, even for delete operations

lp bug: https://launchpad.net/bugs/1180773 fixed

bzr revid: dle@openerp.com-20140423112554-75bpk5k3viroqbh5