Reworking v2 play iterator and fixing some other bugs

Still not working quite right:
* dynamic includes are not adding the included tasks yet
* running roles with tags not quite working right

v2/samples/roles/common/tasks/main.yml

@@ -0,0 +1 @@
+- debug: msg="this is a task from the common role"

v2/samples/roles/role_a/meta/main.yml

@@ -0,0 +1,2 @@
+dependencies:
+- common

v2/samples/roles/role_a/tasks/main.yml

@@ -0,0 +1 @@
+- debug: msg="this is a task from role A"

v2/samples/roles/role_b/meta/main.yml

@@ -0,0 +1,2 @@
+dependencies:
+- common

v2/samples/roles/role_b/tasks/main.yml

@@ -0,0 +1 @@
+- debug: msg="this is a task from role B"

v2/samples/roles/test_role/meta/main.yml

@@ -0,0 +1,2 @@
+dependencies:
+  - test_role_dep

v2/samples/roles/test_role/tasks/main.yml

@@ -1 +1,3 @@
 - debug: msg="here we are in the role, foo={{foo}}"
+- fail:
+  when: foo != "bar"

v2/samples/roles/test_role_dep/tasks/main.yml

@@ -0,0 +1 @@
+- debug: msg="here we are in the role dependency"