ACME modules refactor (#187)

* Move acme.py to acme/__init__.py to prepare splitup.

* Began moving generic code out.

* Creating backends.

* Update unit tests.

* Move remaining new code out.

* Use new interface.

* Rewrite module init code.

* Add changelog.

* Add BackendException for crypto backend errors.

* Improve / uniformize ACME error reporting.

* Create ACMELegacyAccount for backwards compatibility.

* Split up ACMEAccount into ACMEClient and ACMEAccount.

* Move get_keyauthorization into module_utils.acme.challenges.

* Improve error handling.

* Move challenge and authorization handling code into module_utils.

* Add split_identifier helper.

* Move order code into module_utils.

* Move ACME v2 certificate handling code to module_utils.

* Fix/move ACME v1 certificate retrieval to module_utils as well.

* Refactor alternate chain handling code by splitting it up into simpler functions.

* Make chain matcher creation part of backend.

tests/sanity/ignore-2.10.txt

@@ -1,3 +1,4 @@
+plugins/module_utils/acme/__init__.py empty-init
 plugins/module_utils/compat/ipaddress.py future-import-boilerplate
 plugins/module_utils/compat/ipaddress.py metaclass-boilerplate
 plugins/module_utils/compat/ipaddress.py no-assert

tests/sanity/ignore-2.11.txt

@@ -1,3 +1,4 @@
+plugins/module_utils/acme/__init__.py empty-init
 plugins/module_utils/compat/ipaddress.py future-import-boilerplate
 plugins/module_utils/compat/ipaddress.py metaclass-boilerplate
 plugins/module_utils/compat/ipaddress.py no-assert

tests/sanity/ignore-2.9.txt

@@ -1,3 +1,4 @@
+plugins/module_utils/acme/__init__.py empty-init
 plugins/module_utils/compat/ipaddress.py future-import-boilerplate
 plugins/module_utils/compat/ipaddress.py metaclass-boilerplate
 plugins/module_utils/compat/ipaddress.py no-assert