* Obsolete code for included tests has been removed
* The engine uses a proper lexer and is much simplified
* An inline test in the middle of the file now only "sees" the file up to that
point. This fixes an issue where we had spurious errors when a type error was
added at the end of a file, and it would pop up in tests before it. This makes
files including many tests much more practical.
* diffing and resetting the tests has been reintroduced (done at the moment in
Ninja, but for more control (count number of failed tests, etc.) we could put it
back into Clerk at some point
* The Catala CLI can now take an input from stdin (with the possibility to link
a (possibly fake) on-disk file for error reporting and file locations ; this
is useful for running tests)
