Replacement of the base class from "book" to "memoir"

— Now the base class is “memoir”, which is much more flexible and
configurable than “book”.
— Added support for the “bwl-FU” bibliography style, i.e., “author
(year)”.  If more than two authors, replace with just one and add “et
al”.
— No more need of subfigure (direct support by memoir).
— Support for the “linkscolor=color” option
— Support for sending options to the memoir base class with
“memoir={list_of_options}”
— Removed many classes whose functionalities are now provided by the
memoir base class
— Proper configuration of the “palatino” font
— Added support for the “draft” option in the memoir. If present,
replaces the “YEAR, MONTH” by “Draft: TODAY’S_DATE”