* add doctypes allowed to group items, average the rate
* add check field to group items during print
* call common before_print in delivery note
* fix precision issue while calculating average
* add new fields to Supplier Master:
- on_hold: To signal the Customer is blocked from completing certain transactions
- hold_type: 3 options - All, invoices and payments
* sanitize `on_hold` field input
* show hold status in list view
* add `release_date` field to Supplier Master:
- specifies the date when transaction restraint will be removed
* reset release date if supplier is not on hold
* add validation to stop transactions when Supplier is blocked
* add test cases
* return empty list for outstanding references if supplier is blocked
* block make button:payment if supplier is blocked
* adjust test cases
* PEP 8 clean up
* more tests
* adds new fields to Purchase Invoice:
- release_date: once set, invoice will be on hold until set date
- hold_comment: so user can add comment pertaining to why invoice is on hold
* implement individual purchase invoice on hold logic
* allow user to change release date
* update manual
* final cleanup including more validation and tests
* update supplier manual
* make default for release_date argument todays date
* remove Auto Repeat added by mistake
* add on_hold_field to purchase invoice
* add 'On Hold' or 'Temporarily on Hold' status for purchase invoice in list view
* implement explicit payment hold in purchase invoice
* update manual
* add dialog for saving comment
* bug fix, refactor, clean up
* more test cases
* add mode of payment field to Payment Term
* add mode of payment field to Payment Terms Template Detail
* add mode of payment field to Payment Schedule
* add mode of payment in `get_payment_term_details`
* pass bill_date as parameter and calculate due_date on that basis
* calculate payment_schedule on the basis of bill_date if present else posting_date
* add bill_date as an argument to get_party_details
* pass bill_date on supplier trigger in purchase invoice
* Patch: Create Payment Terms based on default credit days set in company and use it while setting due_date
* Payment Terms patch for credit days defined in customer group
* validate schedule dates in non-invoice documents
* change query for orders
* take care of orders with/without payment schedule
* clean up, refactor, PEP8
