ubuntu-cpc: Allow comments in series files and add comments

The addition of disk-image to series files in a prior commit required
some explanation.  Without comment support in series files that was
not possible.  This patch adds support for comments and adds those
comments as well.

live-build/ubuntu-cpc/hooks.d/base/series/root-dir

@@ -1,2 +1,3 @@
+# Include disk-image to ensure livecd.ubuntu-cpc.ext4 is consistent
 depends disk-image
 base/create-root-dir.binary

live-build/ubuntu-cpc/hooks.d/base/series/squashfs

@@ -1,3 +1,4 @@
+# Include disk-image to ensure livecd.ubuntu-cpc.ext4 is consistent
 depends disk-image
 depends root-dir
 base/root-squashfs.binary

live-build/ubuntu-cpc/hooks.d/base/series/tarball

@@ -1,3 +1,4 @@
+# Include disk-image to ensure livecd.ubuntu-cpc.ext4 is consistent
 depends disk-image
 depends root-dir
 base/root-xz.binary

live-build/ubuntu-cpc/hooks.d/make-hooks

@@ -161,7 +161,7 @@ class MakeHooks:
             with open(series_file, "r", encoding="utf-8") as fp:
                 for line in fp:
                     line = line.strip()
-                    if not line:
+                    if not line or line.startswith("#"):
                         continue
                     m = re.match(r"^\s*depends\s+(\S+.*)$", line)
                     if m: