Make package namespace self-contained

[arcresu]

These are the minimal changes necessary to make R CMD check pass. By explicitly specifying the namespace of functions from dependencies, users no longer have to attach the dependencies of epifish themselves. This means that a bit of boilerplate can be removed from the examples in the documentation in future.

The use of the .data pronoun is the documented way to silence warnings in R CMD check (which doesn't know about tidy evaluation and data masking) but as far as I know doesn't actually have any effect beyond that.

In any case, these changes do not affect anything at all about what the code does. While it looks like new dependencies on rlang and magrittr are added, these were already there implicitly via the usage of dplyr, so this just makes it explicit to keep R happy.