Changes menuPath location of demo plugins

Update documentation url to readthedocs
Put card names as final static String fields
Changes location of commands in menubar, hopefully will be clearer with nested menus
Attempt to fix a NPE in overlay display
Adds a warning in distribute spacing when not enough slices are selected
Update bdv-playground dependency to allow for nested menus

pom.xml

@@ -107,7 +107,7 @@
 		<main-class>ch.epfl.biop.abba.ABBALaunchMouse</main-class>
 
 		<!-- bdv playground related dependencies -->
-		<bigdataviewer-playground.version>0.10.3</bigdataviewer-playground.version>
+		<bigdataviewer-playground.version>0.10.4</bigdataviewer-playground.version>
 		<bigdataviewer-image-loaders.version>0.8.1</bigdataviewer-image-loaders.version>
 		<bigdataviewer-biop-tools.version>0.10.4</bigdataviewer-biop-tools.version>
 		<bigdataviewer-selector.version>0.2.7</bigdataviewer-selector.version>

src/main/java/ch/epfl/biop/atlas/aligner/MultiSlicePositioner.java

@@ -676,6 +676,8 @@ public void equalSpacingSelectedSlices() {
                 indexNextKey++;
             }
             new MarkActionSequenceBatchAction(this).runRequest();
+        } else {
+            warningMessageForUser.accept("Can't distribute spacing", "You need to have at least three slices selected.");
         }
     }
 

src/main/java/ch/epfl/biop/atlas/aligner/command/ABBADocumentationCommand.java

@@ -19,7 +19,7 @@ public class ABBADocumentationCommand implements Command {
     @Override
     public void run() {
         try {
-            ps.open(new URL("https://biop.github.io/ijp-imagetoatlas/"));
+            ps.open(new URL("https://abba-documentation.readthedocs.io/"));
         } catch (IOException e) {
             e.printStackTrace();
         }