Implements the remove condition command and its tab completer

src/main/java/net/knarcraft/paidsigns/container/PaidSign.java

@@ -137,4 +137,13 @@ public class PaidSign {
         this.conditions.put(line, new PaidSignCondition(stringToMatch, executeRegex, ignoreCaseBoolean, ignoreColorBoolean));
     }
 
+    /**
+     * Removes a condition from this paid sign
+     *
+     * @param line <p>The sign line the condition belongs to</p>
+     */
+    public void removeCondition(short line) {
+        this.conditions.remove(line);
+    }
+
 }