Adding "Last edited by" for observations

.../vips/logic/controller/servlet/ObservationController.java

.../nibio/vips/logic/controller/session/ObservationBean.java

src/main/java/no/nibio/vips/logic/entity/Observation.java

...ources/no/nibio/vips/logic/i18n/vipslogictexts.properties

...ces/no/nibio/vips/logic/i18n/vipslogictexts_bs.properties

...ces/no/nibio/vips/logic/i18n/vipslogictexts_hr.properties

...ces/no/nibio/vips/logic/i18n/vipslogictexts_nb.properties

...ces/no/nibio/vips/logic/i18n/vipslogictexts_sr.properties

.../no/nibio/vips/logic/i18n/vipslogictexts_zh_CN.properties

src/main/webapp/templates/observationForm.ftl