* renamed HasSourceBase to HasSourceCountBase to reflect function, and because HasSourceBase is changed to be more widely used
* consequent renaming of filters for various object types
* changed source filters to a new 'Citation/source filters' category
* added Citation/_HasSource to check whether Citation refers to a Source with particular properties
* added Person/_HasCitation, Event/_HasCitation and Family/_HasCitation to check whether object refers to a Citation with particular properties
* updated Citation/_MatchesSourceFilter
* updated Rules/_MatchesSourceConfidenceBase
* updated Rules/_MatchesSourceFilterBase
* updated Citation object and citationbase.py for source references
* updated Person/_HasSourceOf
* updated comments in Filters/Rules/__init__.py to document how the various rules are used.
svn: r18339
5e0c4d074a