cast customer fields id to int + update example.php file to show usag…

…e of upload + custom_fields

fix edit issue method not compatible with custom_fields

add issue custom_fields handing + fix casting bug (Project+Version api)

add upload for issues

add upload for attachments

new param to user->all()

fixes listing() methods for Project and Version

add some missing entry points + add optional GET params attributes + …

…minor refactoring

add support for groups, issue relationships, project memberships

possibility to set port number and ssl certificate check