Update namespace

[MarkMc1089]

There were several problems, which this PR fixes.

1. Some functions had duplicated names, e.g. both a DB and a df version but named identically.
2. Some functions were not exported, e.g. @export specified in code but no entry in NAMESPACE. This prevented them being used.
3. Some functions did not have man pages, or the man page was not up-to-date. Not critical, but running the documentation update to fix (2) fixed this as anyway.
4. Package contained a .Rprofile, which was used in favour of my own (and others' own profile). Deleted, as it was preventing my personal R package folder being added to path.

Most functions have both a lazy table and dataframe version. It would make sense to have a single exported function for each use case, which then calls the appropriate version. This could be added very easily.