Added VersionInstaller#isValidVersion

src/main/java/de/gnmyt/mcdash/api/installer/VersionInstaller.java

@@ -13,6 +13,14 @@ public interface VersionInstaller {
     Logger LOG = new Logger(VersionInstaller.class);
     OkHttpClient client = new OkHttpClient();
 
+    /**
+     * Checks if a specific version of a software is valid
+     * @param software the software
+     * @param version the version
+     * @return <code>true</code> if the version is valid
+     */
+    boolean isValidVersion(String software, String version);
+
     /**
      * Installs a specific version of the minecraft server software
      *