Regen schema to pick up missing APIs

Due to some portions of the API living in a different location in the
Juju source, they were missed.  The schema gen code has been factored
out into its own repo (https://github.com/juju/schemagen) and the
missing APIs fixed.

Makefile

@@ -1,6 +1,7 @@
 BIN := .tox/py35/bin
 PY := $(BIN)/python3.5
 PIP := $(BIN)/pip
+SCHEMAGEN := $(shell which schemagen)
 
 clean:
 	find . -name __pycache__ -type d -exec rm -r {} +
@@ -11,6 +12,10 @@ clean:
 	tox -r --notest
 
 client:
+ifndef SCHEMAGEN
+	$(error "schemagen is not available, please install from https://github.com/juju/schemagen")
+endif
+	schemagen > juju/client/schemas.json
 	$(PY) -m juju.client.facade -s juju/client/schemas.json -o juju/client/_client.py
 
 test: