DS-4107 Improve variable naming

.../modify-item-overview/modify-item-overview.component.html

...ts/metadata-uri-values/metadata-uri-values.component.html

...ents/metadata-uri-values/metadata-uri-values.component.ts

...components/metadata-values/metadata-values.component.html

...d-components/metadata-values/metadata-values.component.ts

src/app/+item-page/full/full-item-page.component.html

...ts/specific-field/item-page-specific-field.component.html

...specific-field/title/item-page-title-field.component.html

...nts/specific-field/uri/item-page-uri-field.component.html