Make libsawtooth optional
This change makes the libsawtooth dependency optional.  Only the
splinter-service dependency requires it.
@@ -43,6 +43,7 @@ transact = { version = "0.3.14", features = ["sawtooth-compat", "state-merkle-sq
[dependencies.sawtooth]
version = "0.6.7"
+optional = true
default-features = false
features = ["lmdb", "transaction-receipt-store"]
@@ -87,5 +88,5 @@ lmdb = []
postgres = ["diesel/postgres", "diesel_migrations", "log", "sawtooth/postgres", "transact/postgres"]
rest-api = ["futures", "splinter/rest-api"]
rest-api-actix = ["actix-web", "splinter/rest-api-actix"]
-splinter-service = ["log"]
+splinter-service = ["log", "sawtooth"]
sqlite = ["diesel/sqlite", "diesel_migrations", "log", "sawtooth/sqlite", "transact/sqlite"]
