Adds a copySign command and stuff

Adds a new copySign command that copies all info about a sign, including current lines, placeholders, waxed state, dye for each side, and glow state for each side.
Renames editSign to setSignLine to avoid collision with EssentialsX's editSign
Reduces viewSign to a single command
Makes viewSign display the looked at sign, instead of creating a session
Adds some additional messages
Adds missing documentation to the README

src/main/java/net/knarcraft/placeholdersigns/config/PlaceholderSignMessage.java

@@ -13,11 +13,6 @@ public enum PlaceholderSignMessage implements TranslatableMessage {
      */
     SUCCESS_CLICK_SIGN_TO_EDIT,
 
-    /**
-     * The message to display when waiting for a sign selection (view)
-     */
-    SUCCESS_CLICK_SIGN_TO_VIEW,
-
     /**
      * The message displayed when a player tries to edit a waxed sign without the necessary permission
      */
@@ -42,6 +37,31 @@ public enum PlaceholderSignMessage implements TranslatableMessage {
      * The string displayed when a sign property is denied
      */
     SIGN_PROPERTY_DENY,
+
+    /**
+     * The message displayed when a player command is used from the console
+     */
+    ERROR_PLAYER_ONLY,
+
+    /**
+     * The message to display when the player is not looking at a sign, which is required
+     */
+    ERROR_NOT_LOOKING_AT_SIGN,
+
+    /**
+     * The message displayed when ready to paste a sign
+     */
+    SUCCESS_CLICK_SIGN_TO_PASTE,
+
+    /**
+     * The message displayed when a sign is successfully pasted
+     */
+    SUCCESS_SIGN_PASTED,
+
+    /**
+     * The message displayed when a protection plugin cancels the sign change event
+     */
+    ERROR_CANCELLED_BY_PROTECTION,
     ;
 
     @Override