[IMP] add the test file and help docs for anglo_saxon
[IMP] code improve
[IMP] add the test case for anglo_saxon sale product
[IMP] add the test cases
[MERGE] merge with trunk
[IMP] add new test cases
[IMP] improve code
[IMP] change the name of purchase order
[IMP] improve codes
[IMP] change category
[IMP] add prefix 'X' to the accounts code
[MERGE] merge with latest trunk
[MERGE] account_anglo_saxon: added yaml test + doc files