Paging of Pubmed search results not updating between searches

[kkh451]

The paging of Pubmed search results is not being performed correctly e.g. a search returning > 10 pages
of results only had 1 result on the first page. This may be because the paging is not updating between searches.

[workyjim]

Require specific search term to test properly, but likely due to ebi service returning results from multiple sources. Have tested potential fixes but ebi service does not behave as expected; investigation continues.

[workyjim]

Merged into #29