Three small changes (copyright, template.js copyright, and tildetidy target)

a.) Cleaned up copyright language to match conventions.
(I used the memoir document class documentation as a reference, but
 these conventions are common throughout publishing)

   * The (c) symbol has no legal meaning. Only the word "Copyright" and
     an encircled lowercase c are appropriate. So the word "Copyright"
     was placed before each (c).

   * Each (C) was changed to (c).

   * Kris uses the correct symbols in copyright notices, but those
     symbols can be problematic in terminal-mode editors. Added the word
     "Copyright" as well.

   * Replaced colons/spaces after years with the word "by."

b.) Added a copyright notice to common/content/template.js. It was
    missing one entirely. Please correct if it doesn't need one or if the
    copyright isn't held by Martin.

c.) Also added a "tildetidy" target to Makefile common that includes a
    version of the find line from the existing "clean" target (however,
    this version uses "rm -fv" instead of "rm -f").

common/Makefile.common

@@ -39,7 +39,7 @@ ASCIIDOC = asciidoc
 
 #### rules
 
-.PHONY: all help info doc jar xpi install clean distclean $(JAR)
+.PHONY: all help info doc jar xpi install clean distclean tildetidy $(JAR)
 all: help
 
 help:
@@ -85,6 +85,10 @@ distclean: clean
 	@set -e; for locale in $(LOCALES); do $(MAKE) -C clean; doc; done
 	rm -rf ${BUILD_DIR}
 
+tildetidy:
+	@echo "Removing vim backup files..."
+	find . -name '*~' -exec rm -fv {} \;
+
 #### xpi
 
 $(XPI): $(JAR)