#40 fix better error messages

[simonmitchell]

Description

Makes AnyCustomisableRecoverableError conform to LocalizedError so better error messages are provided to users of ThunderRequest

Related Issue

#40

Motivation and Context

Solves bad/non-verbose errors in apps!

How Has This Been Tested?

Has been tested by pointing Blood at this branch of ThunderRequest

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.