Possibility to load all data-sizes into datastore

[stefina]

It would be great if we had a possibility to configure xloader to load all sizes of data into the datastore.

Right now, the default value for ckanext.xloader.max_content_length is 1GB which makes sense in my eyes but I would like to add a way to have no limit at all.

@davidread do you have concerns about my idea? I was thinking to maybe check if ckanext.xloader.max_content_length was set to 0 we would just go forward and load the data.

If anyone has concerns or a better idea to implement this, let me know. If there is interest/no backlash, I will hopefully be able to spend some time on this next month.