Generate functor to read a property

Given the dbus member class for an interface and property hosted by
inventory manager, generate the getProperty functor for retrieving that
property from inventory. This ability is only supported when using the
`PropertyIs` functor to compare a property within inventory to a given
value before triggering an action.

Example yaml:
filters:
    - name: propertyIs
      service: xyz.openbmc_project.Inventory.Manager
      path: /system/chassis
      interface: xyz.openbmc_project.Inventory.Decorator.CoolingType
      property: WaterCooled
      value:
          value: true
          type: boolean
      dbusMember: "sdbusplus::xyz::openbmc_project::Inventory::\
                Decorator::server::CoolingType"

Generates:
make_filter(functor::propertyIs(
    "/system/chassis",
    "xyz.openbmc_project.Inventory.Decorator.CoolingType",
    "WaterCooled",
    true,
    "xyz.openbmc_project.Inventory.Manager",
    make_get_property<>
    (
        functor::getProperty<sdbusplus::xyz::openbmc_project::
            Inventory::Decorator::server::CoolingType>
        (
            "/system/chassis",
            "xyz.openbmc_project.Inventory.Decorator.CoolingType",
            &sdbusplus::xyz::openbmc_project::Inventory::
                Decorator::server::CoolingType::getPropertyByName,
            "WaterCooled"
        )
    )
))

Tested:
    Code generated as expected with service name given
    Code generated as expected without service name given

Resolves: openbmc/phosphor-inventory-manager#1

Change-Id: I5600854a1b0b9ce3e1511d3bcd9a452d6b1107ba
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/example/events.d/match1.yaml b/example/events.d/match1.yaml
index 3763093..6246dbd 100644
--- a/example/events.d/match1.yaml
+++ b/example/events.d/match1.yaml
@@ -78,8 +78,19 @@
 
     - name: startup event example
       description: >
-          Create /createme3 at startup.
+          Create /createme3 at startup if ExampleProperty1 on /changeme
+          equals changed.
       type: startup
+      filters:
+          - name: propertyIs
+            path: /changeme
+            interface: xyz.openbmc_project.Example.Iface1
+            property: ExampleProperty1
+            value:
+                value: changed
+                type: string
+            dbusMember: "sdbusplus::xyz::openbmc_project::Example::\
+                server::Iface1"
       actions:
           - name: createObjects
             objs: