Manually set exports

[coatless]

Issue:

Any function added to the package must have some form of documentation or be flagged as internal because the NAMESPACE file is configured to automatically export all functions in the package via exportPattern("^[[:alpha:]]+") rule. This is particularly problematic as the feature set of this package grows.

Solution:

Use the roxygen2's @export tag to individual select functions to be exported and, therefore, checked.