Bug fixes

Bug fixes and improvements to the development mode.
A field providing the currently accessed url.

Fixed issue with payment cancellation form.
Addressed multiple Dependency Injection issues.
Improved module API documentation.
Improved constructor method in GoCardlessPartner class.
Improved coding standards throughout in compliance with PHPCS.

#2 Fix a type declaration error.

Issue #3086110 by flocondetoile: Fix the default value for the type url of a micro site
Issue #2910444 by flocondetoile: Automated tests
Issue #3052242 by manu manu, flocondetoile: Allow to disable the site url DNS check
Issue #3051467 by manu manu, flocondetoile: Increase micro site name field max length
Issue #3046759 by flocondetoile, Jyhaire: Should not delete Site-type while used
Issue #3045973 by flocondetoile: Improve and clean up the micro site constraint
Issue #3035936 by flocondetoile: Front page crash after installation of micro_site

- #2986845: validateCallback may throw exception instead of setting an error
- #3085841: Safely create new algorithm class object in the plugin base