[ms, entity metas] add 'actual source' to entities table / base entity metadata cache. Closes #1767090
this is needed since for entities from 'copy based sources' such as
datafeed, we want entity.cw_metainformation() to return as 'source'
the datafeed source, not the system source (ie the source where the
entity is actually stored).
For both performance and bootstraping reasons, we should store this
information in the `entities` table and in the _type_source cache.
###############################################################################
#
# Put here information about external resources / styles used by your cube,
# or to overides existing UI properties.
#
# Existing properties are available through the `sheet` dictionary available
# in the global namespace. You also have access to a `data` function which
# will return proper url for resources in the 'data' directory.
#
# /!\ this file should not be imported /!\
###############################################################################
# CSS stylesheets to include in HTML headers
# uncomment the line below to use template specific stylesheet
# STYLESHEETS = sheet['STYLESHEETS'] + [data('cubes.%(cubename)s.css')]