New Front page (#172)

* Improve Title page

- Made it full page (almost)
- Added a second page with links to github, license info and hard-copy
  book

* Add an xbb target for the cover page

For some reasons using picture outside float environment confuses the
ebook/dvi building

---------

Co-authored-by: Cedric <ced@awase.ostal>

book/book.tex

@@ -8,17 +8,10 @@
 \title{The Sourdough Framework}
 
 \begin{document}
+\input{cover/cover.tex}
+\titlepage
 
 \frontmatter
-% Title page
-\begin{titlepage}
-\begin{center}
-  \includegraphics[width=\textwidth]{images/cover-page.jpg}
-  Version:
-  \today
-\end{center}
-\end{titlepage}
-
 % \tableofcontents
 \ifdefined\HCode\else\tableofcontents\fi