Move and update degimpify script(s)

* Move and rename `degimpify.sh` script to make it easier to find and use the `degimpify` script.
* Make `degimpify.sh` script use `sed` in place.
* Make `degimpify.sh` script use default directories if none are provided.
* Make `degimpify.sh` script support processing all XPM (Pixmap) files in multiple directories.

Signed-off-by: Emily Mabrey <emabrey@tenacityaudio.org>
Reference-to: https://github.com/tenacityteam/tenacity/pull/407

images/EditButtons/Effects.xpm

@@ -1,5 +1,5 @@
 /* XPM */
-static const char * const Effects_xpm[] = {
+static const char * const Effects[] = {
 "26 24 78 1",
 " 	c None",
 ".	c #FFFFFF",

images/EditButtons/degimpify

@@ -1,10 +0,0 @@
-#!/bin/bash
-# Run this script to take an xpm generated by the gimp and format it for
-# use Audacity
-for arg in $@
-do
-  filename=$(tempfile)
-  cat $arg| sed -e 's/\_xpm\[\]/\[\]/' -e 's/^static char \*/static const char  \*/' > $filename
-  mv  $filename $arg
-
-done