New target description + moving target stuff under "framework"

Changing the way target descriptions work from a static mapping to
something that is dynamically generated and is extensible via plugins.
Also moving core target implementation stuff under "framework".

wa/framework/configuration/tree.py

@@ -0,0 +1,89 @@
+#    Copyright 2016 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class JobSpecSource(object):
+
+    kind = ""
+
+    def __init__(self, config, parent=None):
+        self.config = config
+        self.parent = parent
+
+    @property
+    def id(self):
+        return self.config['id']
+
+    def name(self):
+        raise NotImplementedError()
+
+
+class WorkloadEntry(JobSpecSource):
+    kind = "workload"
+
+    @property
+    def name(self):
+        if self.parent.id == "global":
+            return 'workload "{}"'.format(self.id)
+        else:
+            return 'workload "{}" from section "{}"'.format(self.id, self.parent.id)
+
+
+class SectionNode(JobSpecSource):
+
+    kind = "section"
+
+    @property
+    def name(self):
+        if self.id == "global":
+            return "globally specified configuration"
+        else:
+            return 'section "{}"'.format(self.id)
+
+    @property
+    def is_leaf(self):
+        return not bool(self.children)
+
+    def __init__(self, config, parent=None):
+        super(SectionNode, self).__init__(config, parent=parent)
+        self.workload_entries = []
+        self.children = []
+
+    def add_section(self, section):
+        new_node = SectionNode(section, parent=self)
+        self.children.append(new_node)
+        return new_node
+
+    def add_workload(self, workload_config):
+        self.workload_entries.append(WorkloadEntry(workload_config, self))
+
+    def descendants(self):
+        for child in self.children:
+            for n in child.descendants():
+                yield n
+            yield child
+
+    def ancestors(self):
+        if self.parent is not None:
+            yield self.parent
+            for ancestor in self.parent.ancestors():
+                yield ancestor
+
+    def leaves(self):
+        if self.is_leaf:
+            yield self
+        else:
+            for n in self.descendants():
+                if n.is_leaf:
+                    yield n