Reset column configuration when database changes.  

This is necessary because the header_state blobs break between versions.

Also set up some much nicer column width defaults so it's not such a shock when a users' settings are blown away
Maybe the next step (TODO) is to add a header_state version number and compare.  If someone changes the number of columns, they have to bump the header version number.  In fact we could make it so the header version number is just the last enum in the list of columns and it would work automatically (unless we delete and add the exact same number of columns, which is unlikely)