Consistently use "sentence case" style

Try to be more consistent in how we capitalize things. Both the "Title
Case" and "Sentence case" styles are popular, so either would work.
Google and Mozilla both prefer "Sentence case", so let's follow them.

po/Makefile

@@ -19,7 +19,7 @@ update-js: $(JSONFILES)
 
 update-pot:
 	xgettext --output=noVNC.js.pot \
-		--copyright-holder="The noVNC Authors" \
+		--copyright-holder="The noVNC authors" \
 		--package-name="noVNC" \
 		--package-version="$(VERSION)" \
 		--msgid-bugs-address="novnc@googlegroups.com" \

po/po2js

@@ -1,7 +1,7 @@
 #!/usr/bin/env node
 /*
  * ps2js: gettext .po to noVNC .js converter
- * Copyright (C) 2018 The noVNC Authors
+ * Copyright (C) 2018 The noVNC authors
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by

po/xgettext-html

@@ -1,7 +1,7 @@
 #!/usr/bin/env node
 /*
  * xgettext-html: HTML gettext parser
- * Copyright (C) 2018 The noVNC Authors
+ * Copyright (C) 2018 The noVNC authors
  * Licensed under MPL 2.0 (see LICENSE.txt)
  */