Review dependancies, applications page

[vincentdavis]

I checked all the links and what is there seems correct. Is it complete? I think there are automated tools for discovering dependencies. https://github.com/biopython/biopython.github.io/blob/master/wiki/List_of_applications_executed_via_Biopython.md

[peterjc]

Some clever grep searches for things like subprocess ought to spot any other external tool calls we make, on top of the Bio.Application wrappers etc.