Fixes to AUTHORS

Description

• Fix bug where error message for AUTHORS-check wasn't finding AUTHORS in the right place
• Hide the AUTHORS-check when running make with V=1; just print a message
• Allow author names to have a capitalised first name without dots or spaces
• Update .mailmap

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

Review Status

Closes #591 (closed)

cc @adam-mercer