Remove some tests no longer used

allow Identity baseURL to be set in ApiClient

Remove hardcoded api.xero.com and allow it to be set when initializeing ApiClient class.

bump version

Updates for identity dates, accounting & bankfeeds

Identity
- update and create date issue
 This was accomplished using "LocalDateTime" instead of "OffsetDatetime" and a custom date deserializer class. The OpenApi spec introduced a new vendor extension - x-format at the proprty level which allows for over riding the default datatype used by the type:stirng and format: date.

Accounting
-remove createLinkedTransactions as bulk create is not supported

BankFeeds and Fixed Assets
- add XeroApiExceptionHander for errors when parsing HttpResponses
- Change case for tenant id param to Xero-Tenant-Id
- Headers passed as params are now being set properly.

Move multiple create methods to POST method

Found #bulk while ignored in the Java SDK, it impacted PHP and has been removed in favor of using PUT for single create (object) and POST for multiple create (array of objects).  I know not "RESTful" but one more quirk in the API.

Fixed headers not being set properly

contentType and IfModifiedSince headers are now being set on http requests

remove duplicate enum on Tax Rate Reporting Type

v 3.1.3

Organisation - add ENUM ACCOUNTING_PRACTICE
BrandingTheme - add LogoUrl and TypeEnum
Accounts - add "addToWatchList" attribute

fix maven badge

Update README.md