Do no re-validate parameters for existing stacks

This patch disables validation of stack parameters values when
loading existing stacks from the database. The old behavior was
to always validate stack parameter values when initializing a
Stack object. However, this causes problems especially with
custom constraints when a constraint could be fulfilled during
stack creation but cannot be fulfilled at a later point (e.g.
when a flavor or keypair has been deleted). In such a case,
the existing stack became completely unusable.

This patch changes the behavior to not do parameter validation
for existing stacks. The assumption is that validation at stack
creation time should be sufficient to make sure the stack is valid,
so only valid stacks end up in the database. Therefore, validating
parameters again when loading stacks is not really required.

Change-Id: I0947c2dcfb9db4c81b07de582aab86f262d0c008
Closes-Bug: #1314401
Remove mention of update_allowed_keys

Some tests still set this ignore property. Stale comments have
also been deleted.

Change-Id: I866b251e0235ca530fc066a4beeadaa743108091
All resources to use Schema update_allowed

No in-tree resources now use the property update_allowed_properties

Change-Id: I63bb9b5c3fab6f898619cddc3f64f00820fe4f12
Use str_to_num for Number parameter

Current implemenation method 'value' convert all input parameters. But
should ignore type Number, because it may round value with float type.
Also this logic is already implemented in str_to_num method. This patch
forces NumberParam class to use str_to_num in value method.

Closes-Bug: #1323649

Change-Id: I7333cb4d6641d886cffb4812ceaa58db8d86c135
Merge "Do no re-validate parameters for existing stacks"
Merge "Use str_to_num for Number parameter"
Merge "Remove mention of update_allowed_keys"
Merge "All resources to use Schema update_allowed"