dials.show: Add summary table for reflection flags
dials.show: Add summary table for reflection flags

Added a phil parameter ‘show_flags’, which prints out a summary of the 
counts of each of the reflection flags in the tables. Also, changed the
’flags’ column to not show the (meaningless) mean/max/min values for
this column.
dials/dials,dials/dials,dials/dials,dials/dials,dials/dials