vm/file-editor: mask some charracters in filename (#406)
vm/file-editor: mask some charracters in filename (#406)

mimeopen passes wrong filename to the editor/viewer when filename contains '#'.
So mask this (replace _) and some other non-alpha-numeric characters.

marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin