XML export driver: fix export options
Merge pull request #1214 from Fedik/fix-xml-export-options

XML export driver: fix the options export
fix instantiation of embedded object in ReflectionEmbeddedProperty
#1213 - DDC-3437 - refactoring tests to support embeddable class name != embeddable class property declaring class
#1213 - DDC-3437 - adding relevant test assets
#1213 - DDC-3437 - integrating new tests into the pre-existing data-provider
#1213 - DDC-3437 - removing redundant test method
#1213 - DDC-3437 - removing unused test assets
#1213 - DDC-3437 - renaming variables/alignment/clarifications in docblocks
Merge branch 'hotfix/#1213-DDC-3437-reflection-embeddable-with-abstract-embeddable-ancestor'

Close #1213
Checks key exists rather than isset

If the default value is set to `null`, `isset` will return `false` even though the key is actually there for a reason.
Added test that passes following previous commit
#1202 - simplified test and test asset
Merge branch 'hotfix/#1202-nullable-options-should-be-allowed'

Close #1202
test for #1214, XML export the field options
#1214 #1216 - adding `@group` annotation for newly introduced test cases
Merge branch 'hotfix/#1216-tests-for-#1214-xml-driver-exporting'

Close #1216
Close #1214