Check for facet results less than or equal to 1, if so, do not display the block, since it's redudant data.  Rather than using a seperate module or an additional setting, I found it easier to just clear the facet content, since OS knows if the block content is empty to not render the block.  Also cleaned up the Filter By Post Date title to match the other two facets.  #667
Merge pull request #1894 from openscholar/667-remove-single-result-facet

#667 Don't display a facet with only one result.  

Merging the issue mentioned will be handled in a seperate PR for #1732