Resolve test coverage (#3947)

* test coverage for __init__ and __call__

* test coverage for metadata resolve and coverage

* partial test coverage for metadata mapping

* python 3.6 workaround for deepcopy of mock.sentinel

* test coverage for Resolve._free_mapping

* test coverage for Resolve convenience methods

* add test stub for Resolve._metadata_mapping

* fix Test__tgt_cube_position

* test coverage for shape

* test coverage for _as_compatible_cubes

* test coverage for Resolve._metadata_mapping

* test coverage for Resolve._prepare_common_dim_payload

* test coverage for Resolve._prepare_common_aux_payload

* test coverage for Resolve._prepare_points_and_bounds

* test coverage for Resolve._create_prepared_item

* test coverage for Resolve._prepare_local_payload_dim

* test coverage for Resolve._prepare_local_payload_aux

* test coverage for Resolve._prepare_local_payload_scalar + docs URL skip

* test coverage for Resolve._prepare_local_payload

* test coverage for Resolve._metadata_prepare

* added docs URL linkcheck skip

* test coverage for Resolve._prepare_factory_payload

* test coverage for Resolve._get_prepared_item

* review actions

* test coverage for Resolve.cube

Author: bjlittle

docs/iris/src/conf.py

@@ -269,6 +269,8 @@ def autolog(message):
     "http://schacon.github.com/git",
     "http://scitools.github.com/cartopy",
     "http://www.wmo.int/pages/prog/www/DPFS/documents/485_Vol_I_en_colour.pdf",
+    "https://software.ac.uk/how-cite-software",
+    "http://www.esrl.noaa.gov/psd/data/gridded/conventions/cdc_netcdf_standard.shtml",
 ]
 
 # list of sources to exclude from the build.