proposing to add collapse/expand function to metadata sections

[Lauracri]

v2.0.1-alpha
/edi/RNDT_dataset_v4.00_newFormat.xml
/edi/SensorML20_lightweight_v1.00_forLTER_newSchema.xml

It would be really useful to collaps and expand the sections of metadata.
It can be done by selecting the related section on the menu list, and by using dedicated icons on the section title