* Add new gst field in Taxes and Charges template - is_inter_state
* Add a patch
* Add a regional function to fetch taxes on the basis of GSTin
* Add regional function to hooks.py
* Fetch taxes for Purchase Invoice on the basis of Supplier GSTIN
* Fixes in the setup.py for India region
* Set is_inter_state field
For the existing Taxes and Charges templates, if an account_head with igst account (which is set in GST Settings) is found, set the checkbox and also check if it doesn't have a cgst account.
* Fix as per review comment