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").

Makefile

@@ -1,6 +1,6 @@
 
 DIRS = vimperator muttator
-TARGETS = clean distclean doc help info jar release xpi
+TARGETS = tildetidy clean distclean doc help info jar release xpi
 .SILENT:
 
 $(TARGETS:%=\%.%):