Switch to Emacs Muse for website and manual

Switch to Emacs Muse for website and manual

This commit records all the changes made to the way the webpage and the
manual are created: the muse files are added, the html headers, the new
images and the css files. The old texinfo document and index.html are
removed, and also the old images.

The script make-ebib-release.sh has not been updated yet.

	new file:   manual/ebib-manual-header.html
	new file:   manual/ebib-manual.css
	new file:   manual/ebib-manual.muse
	deleted:    manual/ebib-manual.texinfo
	new file:   webpage/ebib-xhtml-header.html
	new file:   webpage/ebib.css
	deleted:    webpage/graphics/br-indep.gif
	deleted:    webpage/graphics/ebib.jpg
	deleted:    webpage/graphics/strings.jpg
	deleted:    webpage/graphics/tn_ebib.jpg
	deleted:    webpage/graphics/tn_strings.jpg
	new file:   webpage/images/ebib-1.png
	new file:   webpage/images/ebib-2.png
	new file:   webpage/images/muse-abailly.png
	new file:   webpage/images/tn_ebib-1.png
	new file:   webpage/images/tn_ebib-2.png
	new file:   webpage/images/valid-css-blue.png
	new file:   webpage/images/valid-xhtml10-blue.png
	deleted:    webpage/index.html
	new file:   webpage/index.muse