tests: Additional inventory tests for Locations and MovementTypes
Fix #8 and Fix#9: Categories validation, and paging

- Added CRUD test for categories api
- Fix #8 paging now will allow the return of all records
- Fix #9 inventory_account is now checked for on add and edit.
Fix #11: include path for taxgroups and taxtypes
tests: Added tests for /modules/api/taxtypes and modules/api/taxgroups
Fix #13 and #14: Customers delete and Customers add

- Customer add now works
 * Removed use of id in index.php
- Customer delete now works
 * Added additional include file
- Added Customer_Test for CRUD tests
Fix #16 and #17: Suppliers list and Suppliers add with tests

- Fix #17 add supplier now works
 * Remove use of $id in index.php
- Fix #16 added a list endpoint to list all suppliers
- Added CRUD tests
Code formatting
feature/sales: Added CRUD tests

- Adding default branch makes the api consistent with the FA ui.
- This is necessary for testing of the sales api
Merge pull request #21 from cambell-prince/feature/Sales

feature/sales: Tests and enhancements for sales api
Merge pull request #18 from cambell-prince/feature/Suppliers

Fix #16 and #17: Suppliers list and Suppliers add with tests
Merge pull request #10 from cambell-prince/feature/Category

feature/category CRUD tests for modules/api/category and other apis
Merge pull request #12 from cambell-prince/bug/11

bug/11 Fix for incorrect include path in taxtypes and taxgroups
Fix #19: Add ItemCost tests and fix item cost update
Code formatting
feature/assets: Make assets api optional in cases where the module is not installed.

- assets api now returns 404 if the module is not installed.