replace startDate + dateRange with start and end date

The new datetimepicker can be used to specify date ranges. We no longer
need to define a start date and a range. This simplifies the code
for zooming and shifting considerably.

pdb-ui/src/main/java/org/lucares/pdbui/domain/PlotRequest.java

@@ -24,8 +24,6 @@ public class PlotRequest {
 
 	private int limit = Integer.MAX_VALUE;
 
-	private String dateFrom;
-
 	private String dateRange;
 
 	private Aggregate aggregate = Aggregate.NONE;
@@ -107,22 +105,11 @@ public class PlotRequest {
 		this.limit = limit;
 	}
 
-	public String getDateFrom() {
-		return dateFrom;
-	}
-
-	public void setDateFrom(final String dateFrom) {
-		this.dateFrom = dateFrom;
-	}
-
 	public String getDateRange() {
 		return dateRange;
 	}
 
 	public void setDateRange(final String dateRange) {
-		if (!dateRange.matches("\\d+ (second|minute|hour|day|week|month)s?")) {
-			throw new IllegalArgumentException(dateRange + " is not a valid range");
-		}
 		this.dateRange = dateRange;
 	}