Off-device library for the power model.

This first CL adds a class, PowerProfile that parses the power
profile xml file into a set of individual *Profile classes, one
for each of the hardware "components."

There will be more to come.  This library will be used to compute
the power model from a batterystats or statsd dump, with abstractions
so clients don't need to know all of the nuances of batterystats'
old versions, or statsd's configs.

Test: atest frameworks/base/tools/powermodel --host
Change-Id: I79802f91234b09539072d10f15534cef391fe04a
diff --git a/tools/powermodel/TEST_MAPPING b/tools/powermodel/TEST_MAPPING
new file mode 100644
index 0000000..c8db339
--- /dev/null
+++ b/tools/powermodel/TEST_MAPPING
@@ -0,0 +1,8 @@
+{
+  "presubmit": [
+    {
+      "name": "powermodel-test"
+    }
+  ]
+}
+