Polish "individuals table" to "individual table" etc. #142

Slight terminology tweak. The upstream uses NodeTable as name of the class and ts.tables.nodes as accessor function. Note the difference in not using s in the first (since it refers to table class) and using it in the accessor function. We should not loose sleep over such details, but good to spot and fix them when we see them. So, let's refer to provenance table (without the s when we add table in the wording) and provenances (with the s when we don't add table in the wording). Should be easy to polish by searching for "table" across the codebase.