[#53] Remove codelist urls

The 'single source of truth' for these is the codelist mapping file:
https://github.com/IATI/IATI-Codelists/blob/master/mapping.xml
Merge remote-tracking branch 'origin/53-remove-codelist-urls' into version-2.01

Conflicts:
	iati-activities-schema.xsd
	iati-common.xsd