v3.0.0

Fix version to better relate to main api v3.
Fix new alternative method for setting connection credentials.
Fix a number of elements on supplier invoice.
Fix date search on offer and order.
Fix problems with contract accrural including renaming rows according to documentation.
Fix delete file and folders.
Fix upload and download memory file data inclduing new properties on file.
Fix new testproject.
Fix a number of new properties, filters etc. on customer, article etc.