Make stepwise configuration writeable

Add schema file and add to writeable array

Tested-by: Verified types change to writeable

Change-Id: Ie089f4e221e2651afb0172a9314130e527728f27
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/src/EntityManager.cpp b/src/EntityManager.cpp
index cd14cc1..9198ee5 100644
--- a/src/EntityManager.cpp
+++ b/src/EntityManager.cpp
@@ -70,8 +70,8 @@
                  {"FOUND", probe_type_codes::FOUND},
                  {"MATCH_ONE", probe_type_codes::MATCH_ONE}}};
 
-static constexpr std::array<const char *, 3> settableInterfaces = {
-    "Thresholds", "Pid", "Pid.Zone"};
+static constexpr std::array<const char *, 4> settableInterfaces = {
+    "Thresholds", "Pid", "Pid.Zone", "Stepwise"};
 using JsonVariantType =
     sdbusplus::message::variant<std::vector<std::string>, std::string, int64_t,
                                 uint64_t, double, int32_t, uint32_t, int16_t,