About: remove the Limitations part

There is no more this limitation. :)
Add changelog HTML structure in changelog.html
Add ChangelogDialogFragment

This DialogFragment will be used to show the HTML changelog.
MainActivity: show the changelog at first launch

And store the SharedPreferences object in a member variable since it is
used in several methods.
Change app name: Données BnF -> Auteurs et œuvres

The english name BnfData will still be used in identifiers.
About: display the app's icon, name and version
strings.xml: replace tabs with spaces
AboutActivity: reword the generalities
AboutActivity: add section to see the changelog
AndroidManifest: version 1.0 (1) -> 2.0 (2)
ExpandableTextView: add OnExpandListener
View* activities: linkify the editorial notes
View* activities: save state of the Exp.TextViews
Fix padding of the 9-patch expand/collapse arrows

It was causing an increase of the height of the TextView when the
background image is set, then hiding some text at the end because of the
mismatch with the measured height without the backgroud image.
Add changelog for versions 1.0 and 2.0