First complete version of the package

Everything works but the internal tools are not really finished (the
"clear session" feature or "configuration" page must not work)
OUPS

Corrections on the README (I copied it from another project :(
New repo name for Composer

New name for the package and for the "WebFilesystem" one
Renaming the package with new GitHub name

Renaming the vendor and package names according to modifications done
on GitHub, and renaming the required "webfilesystem" package too
new piwi github url