Bring across updates to FML in Gusto to the FML branch (#3055)

* port FML changes from gusto

* update docstring style

* fix lint and docstring issues

Author: tommbendall

firedrake/__init__.py

@@ -74,7 +74,6 @@
 from firedrake.checkpointing import *
 from firedrake.constant import *
 from firedrake.exceptions import *
-from firedrake.fml import *
 from firedrake.function import *
 from firedrake.functionspace import *
 from firedrake.interpolation import *
@@ -105,6 +104,7 @@
 from firedrake.ensemble import *
 from firedrake.randomfunctiongen import *
 from firedrake.progress_bar import ProgressBar  # noqa: F401
+from firedrake.fml import *
 
 from firedrake.logging import *
 # Set default log level

firedrake/fml/__init__.py

@@ -1,2 +1,2 @@
-from gusto.fml.form_manipulation_language import *        # noqa
-from gusto.fml.replacement import *                       # noqa
+from firedrake.fml.form_manipulation_language import *        # noqa
+from firedrake.fml.replacement import *                       # noqa