raw_template hot parameter type data migration

Changes were made to the hot syntax which prevent invalid templates
already present in the database from being loaded as part of a stack
list. This database migration forces the parameter schema type to
be lowercase.

Change-Id: Iaa4b16e9b5188e6e99cda95e1c7fb0dc11c206f7
Partial-Bug: #1274288
Add validation to KeyPair resource

Make sure a keypair with the name passed to the KeyPair resource doesn't
already exist.

Closes-Bug: #1278532
Change-Id: I466e035e207def85ded5b2978a7da8cfe5ffb6a8
Add StackResource specific preview behavior

This allows previewing a StackResource not as a single resource, but as
resources within a stack.  In order to do that, resources that inherit
from StackResource must override both ``child_template`` and
``child_params`` methods to allow the stack to be parsed.  If any of
these methods is missing, the preview will default to being just the
StackResource itself, and will be returned as a single resource.

Implements: blueprint preview-stack (partial)
Change-Id: I03be7e58a6809f5061546a469b69165d6ca70a30
Add preview for NestedStack

Override ``child_template`` and ``child_params`` to allow previewing of
NestedStack as a group of resources.

Implements: blueprint preview-stack (partial)
Change-Id: I3acde4ccc31731aee1209c747fdbcc4446be63bc
Add preview for ResourceGroup

Override ``child_template`` and ``child_params`` to allow previewing of
ResourceGroup as a group of resources.

Implements: blueprint preview-stack (partial)
Change-Id: I165e31dcc1be5eddf00caa4209b1ff027b129cc6
Add preview for InstanceGroup

Override ``child_template`` and ``child_params`` to allow previewing of
InstanceGroup as a group of resources.

Implements: blueprint preview-stack (partial)
Change-Id: I821ac72e11921964acd5d8f1dd33a302edf3aa8b
Add preview for TemplateResource

Override ``child_template`` and ``child_params`` to allow previewing of
TemplateResource as a group of resources.

Implements: blueprint preview-stack (partial)
Change-Id: I34d81783ecfe2592c8e3759c4e9afc47a8483b94
Revert "Merge "Re-enable lazy translation""

Revert enabling lazy translation, which doesn't work in many places
because we're doing string concatenation.

This reverts commit 1864efa320aadbb4f5503c15345dd363bb3691c1, reversing
changes made to 92e3e3ce74dc1e3f75d51600072227c2e44016a6.

Closes-Bug: #1281644
Change-Id: Iac0be685f8bb60f81715c0dd3dbe35787e38ee39
Merge "Add StackResource specific preview behavior"
Merge "Add preview for NestedStack"
Merge "Add preview for ResourceGroup"
Merge "Add preview for InstanceGroup"
Merge "Add preview for TemplateResource"
Merge "Revert "Merge "Re-enable lazy translation"""
Merge "raw_template hot parameter type data migration"
Merge "Add validation to KeyPair resource"