changed nomacs icon
added folder icon
added ImageUtil
for now there is just getScale() in there but that will change
added IgnoreHiddenFilesFilter to exclude hidden files when using file.getFiles()

the array displays the real thumbs now, but it is still far too slow!
TODO: chache thumbs

	new file:   nomacs/src/org/nomacs/android/nomacs/util/IgnoreHiddenFilesFilter.java
	new file:   nomacs/src/org/nomacs/android/nomacs/util/ImageUtil.java
	modified:   nomacs/ic_launcher-web.png
	modified:   nomacs/src/org/nomacs/android/nomacs/CustomArrayAdapter.java
	modified:   nomacs/src/org/nomacs/android/nomacs/ImageActivity.java
	modified:   nomacs/src/org/nomacs/android/nomacs/ImageBrowserActivity.java