fix: c'tor of ImprovedFormattedTextField form field wasn't... (#94)

...considering the initial value, and was thus always
displaying an empty field (no text)

src/main/java/org/janelia/saalfeldlab/n5/ui/ImprovedFormattedTextField.java

@@ -67,8 +67,9 @@ public ImprovedFormattedTextField(AbstractFormatter formatter) {
 	public ImprovedFormattedTextField(AbstractFormatter formatter, Object aValue) {
 
 		this(formatter);
+		String strValue = aValue instanceof String ? (String)aValue : "";
 		try {
-			setValue(new URI(""));
+			setValue(new URI(strValue));
 		} catch (URISyntaxException e) { 
 			e.printStackTrace();
 		}