Update content_type_detection.rb

reduce size of extractable spreadsheet
OPSK-87 - getting contents from xls and xlsx for search using soffice
fix to is_viewable_content?

is not necessarily viewable just because a pdf exists. In the case of spreadsheets, the pdf generated isn't really suitable to view and we have the spreadsheet explorer views
make max_extractable_spreadsheet_size a configurable setting

rather than being hard-coded
defaults to 10Mb
methods on model to get view and download counts for a resource

removed from view helper method, and instead added to module mixed into isa and assets
moved other stat modules into a new seek/stats namespace
added a Top of the Pops rake task to get top downloads and views
OPSK-87 - updated sunspot search field used for models#matching_data_files
fix to getting the content stats

the logic for the download values for non downloadable items was incorrect and always results in zero
fix for matching models

even though the button has been removed the route is still available and being hit by google.
Fix updates after swticing to soffice for indexing, so need to use content_blobs search field rather than spreadsheet_contents_for_search
Merge branch 'seek-0.22'

Conflicts:
	lib/seek/stats/content_stats.rb