Add 'a' as shortcut to go to change and open reply box

This saves one keystroke when going from a file back to the
change screen to send a reply comment.

CodeMirror seems to be eating the 'a' and refuses to let us
bind to the character there.

Change-Id: I2cfac04cad9a9cebe94913ae9f464894df4c2a7d

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchConstants.java

@@ -40,6 +40,7 @@ public interface PatchConstants extends Constants {
   String illegalNumberOfColumns();
 
   String upToChange();
+  String openReply();
   String linePrev();
   String lineNext();
   String chunkPrev();

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchConstants.properties

@@ -22,6 +22,7 @@ intralineTimeout = Intraline difference not available due to timeout.
 illegalNumberOfColumns = The number of columns cannot be zero or negative
 
 upToChange = Up to change
+openReply = Reply and score
 linePrev = Previous line
 lineNext = Next line
 chunkPrev = Previous diff chunk or comment