Develop metadata dims 2vars

See merge request !92

Bugfix for metadata_dims when more than 1 dat. Unit test is created.

See merge request !90

Develop return vars null reorder

See merge request !89

Add unit tests for checking metadata when using reorder or transform, under the condition that returns_var = NULL/'dat'.

Bugfix for Start() parameter 'path_glob_permissive' and write the explanation in FAQ and Start() header.

Develop roxygen2

See merge request !86

Fix hyperlink for how-to-#16

See merge request !87