Simplify select field type

[txau]

Is your feature request related to a problem? Please describe. In order the reduce the amount of available field types in templates we could simplify select and multi-select fields into a single field type.

Describe the solution you'd like The new field could be called "Thesaurus" since this field type works with thesaurus alone (relationship fields are different) and have a configuration option to indicate whether a single option or multiple options are allowed.

Generally speaking, the behavior should that of a multi-select. TBD how the field will behave when it needs to act as a single option select (ie. selecting a new option deselects the previous one, it has some UI hint, etc) (cc @juanmnl )