Other charges at invoice.

#479
Added Other charges field to invoice table.
Added condition to check other charges in invoice table, calculate tax and total of other charges at view single invoice API.
Added other charges to the invoice table to send front end.
Added other charges data to create automatic voucher entry at add and edit invoice API.
Added other charges data to create automatic voucher entry at add and edit invoice API when delivery note is selected.
Added condition to check view single invoice call from print invoice.
Created separate dict data for print single invoice screen.
Made changes to show taxes and invoice total at view list of invoice. Added other charges field to invoicebin table. Added condition to check other charges in invoicebin table, calculate tax and total of other charges at view single cancel invoice API. Made changes to show taxes and invoice total at view list of cancel invoice.
Added othchargeval field to product table to specify other charges.
Made changes at fetch all product API to fetch only products and services not other charges.
Create new API to fetch all products, services and other charges for edit product, list of all products screen.
For gkwebapp :- https://gitlab.com/gnukhata/gkwebapp/merge_requests/1178