Implement multifile downloads

Author: kylstevenson

src/main/java/io/github/jpmorganchase/fusion/Fusion.java

@@ -615,13 +615,14 @@ public void download(
             String url = null;
             try {
                 url = String.format(
-                        "%scatalogs/%s/datasets/%s/datasetseries/%s/distributions/%s?file=%s",
-                        this.rootURL,
-                        catalogName,
-                        dataset,
-                        seriesMember,
-                        distribution,
-                        URLEncoder.encode(fileName, "UTF-8"));
+                                "%scatalogs/%s/datasets/%s/datasetseries/%s/distributions/%s?file=%s",
+                                this.rootURL,
+                                catalogName,
+                                dataset,
+                                seriesMember,
+                                distribution,
+                                URLEncoder.encode(fileName, "UTF-8"))
+                        .replace(".", "%2E");
 
             } catch (UnsupportedEncodingException e) {
                 throw new RuntimeException(e);

src/main/java/io/github/jpmorganchase/fusion/digest/PartChecker.java

@@ -39,7 +39,7 @@ public void update(int bytesRead) throws IOException {
     public void verify(String expectedChecksum) throws IOException {
         String calculatedChecksum = digestProvider.getDigest();
 
-        if (!Objects.equals(expectedChecksum, calculatedChecksum)) {
+        if (expectedChecksum != null && !Objects.equals(expectedChecksum, calculatedChecksum)) {
             log.error(
                     "Corrupted stream encountered, failed to verify checksum [{}] against calculated checksum [{}]",
                     expectedChecksum,