Delegate DSL method values to their superclass

When inheriting from +Resource::LWRPBase+, the +default_action+ and +actions+ attributes are set as class instance variables. In Ruby's object model, class instance variables are **not** shared with children. So subclassing a resource that extended from +Resource::LWRPBase+ would result in some unexplainable side-effects:

```ruby
class Chef::Resource::Parent < Chef::Resource::LWRPBase
  actions :execute
  default_action :execute
end

class Child::Resource::Child < Chef::Resource::Parent
  # In here, +actions+ and +default_action+ are **not** inherited so they
  # are +nil+!
end
```

This commit tells resources that inherit from LWRPBase to check their superclasses for values if they do not have one on their own.

/cc @opscode/release-engineers @danielsdeleo 
How will we know about those old APIs then? I didn't see any deprecations in the test output. I actually just watched a talk about this at Velocity yesterday. So-called "tombstones" are the best way to track down technical debt and services that are using this old API. I would rather be annoyed with some warnings about a deprecated API than get "undefined method `valid_actions' for blah". One is a much nicer upgrade path to the other. Given that Chef doesn't use `LWRPBase.valid_actions` anywhere that I could find, I don't see a reason to keep the method around.