Better support for HXL tags

[dickoa]

• Preliminary support for rhxl added
• Better support for HXL e.g automatically reading HXL tagged data
  @dirkschumacher

[dirkschumacher]

👍 What do you mean by better? If you can give more details, it would be easier to see what I can do

[dickoa]

I added a hxl parameters in the read_session function (function that allows to read resource file directly in R) and I use the rhxl package to parse them more effectively.

https://github.com/dickoa/rhdx/blob/master/R/utils.R#L99
https://github.com/dickoa/rhdx/blob/master/R/resource.R#L112

Not directly related to HXL, the main issues I have right now is documenting and also having a consistent API. I can start working on a better doc but if you can test the package in order to improve the api and its usability it would help.

Thanks again.