Move expansion notes

notes/.gitignore

notes/expansion-notes.pdf

notes/expansion-notes.tex

notes/latexmkrc

notes/media/.DS_Store

notes/media/graf.eps

notes/media/graf.ipe

notes/media/l-expn.eps

notes/media/l-expn.ipe

notes/media/local-expansion.ipe

notes/media/m-expn.eps

notes/media/m-expn.ipe

notes/media/m2l-translation.eps

notes/media/m2l-translation.ipe

notes/media/m2m-l2l-translation.eps

notes/media/m2m-l2l-translation.ipe

notes/media/m2m-translation.eps

notes/media/m2m-translation.ipe

notes/media/multipole.ipe