Add support setup default initializers for all deployment

Add support setup default initializers for all deployment

This looks up a new configuration options called `brooklyn.deployment.initializers` (comma separated list). If specified on a Brooklyn instance, all deployments will load and execute these initializers. Theses classes are expected to be `EntityInitializer`, if an error occur (either cast or anything else) then the deployment will fail.

The code will try to:
1. load the class from the default class loader.
2. if (1) fails, it will try to load the class from the `TypeRegistry`. This is to allow execution of custom initializers that might be installed in the catalog later on.
3. if (1) and (2) fails, then the deployment is aborted.