Adjust input files workflow

[werpuc]

The read_hdx() function should return hdx_data class, and it should work for all datafile types.

• implement class
• implement validator
• make sure it is working for all data files.

Origin of the issue: https://github.com/michbur/HaDeX-projects/issues/2

[werpuc]

Currently, the hdexaminer data files are not working, as there is a need to manually curate the data - it is done by update_hdexaminer_file() function.

Question: should we first make the class object, and later change it, using method update_hdexaminer_file? This changes the column type (e.q. FD in Exposure), or should it be somehow replaced?

[werpuc]

Datafile types are described in https://github.com/michbur/HaDeX-projects/issues/23.