Show case properties in the "Case History" table of the Case Export page by default

Previously, you had to check the "show advanced and deleted properties" box to see all properties in the case history table. Now, all of those properties will be shown regardless of whether the box is checked or not. (The "Cases" table is unaffected).

Addresses this ticket:
http://manage.dimagi.com/default.asp?123010#695770
not sure the answer to this question, but it might be cleaner (although admittedly more work) to explicitly tag the fields we care about as "show=True" in this function: https://github.com/dimagi/commcare-hq/blob/master/corehq/apps/export/custom_export_helpers.py#L386 rather than hard code against the actions block. won't be offended if you want to push back on that though.