UI: check field values in dataset table

[idoiamurua]

@xmolero, @eturienzo
When the end-user enters the values for the following fields, the UI module will check that they do not contain the "/" character inside them. These fields may only contain alphanumeric characters:

• dataset.uri_id_part
• dataset.uri_doc_part
• dataset.uri_def_part
• dataset.uri_set_part

The following fields may contain the "/" character inside them:

• dataset.uri_concept_part
• subset.uri_concept_part

The UI will also check that the following two fields cannot be the empty string at the same time. One of them must have a value:

• dataset.uri_doc_part
• dataset.uri_concept_part

[xmolero]

The UI check the values correctly.