Refactor ApplicationType concept

[jvalkeal]

org.springframework.cloud.deployer.admin.core.ApplicationType currently defines source, processor, sink and task. This is something what base deployer admin core would use which means that we can't have hard-coded types as deployer admin core would not know anything about streams.

ApplicationType is generally used:

• as enum to get all possible values, i.e. shell lists all app types (app list)
• dataflow core will mostly shuffle stuff around using ApplicationType
• it's used to check consistency of types given in to various functions

If this concept is changed to be more generic then problems we're facing is illustrated with a simple example. Lets make this type as s single property list.

• deployer-admin needs to define its own defaults, which probably would be task and some generic boot app version. Lets use generic for now.
• dataflow server impl would then need to reliably override this setting which kinda gets awkward.
• In a same way shell impls would need to re-define these

[jvalkeal]

I was kinda playing with ideas what we have in MediaType/MimeType as those know type and subtype.

If we remove hardcoded enumeration of possible app types, then base system defines some generic ones which might be plain generic boot apps and tasks. Dataflow should then add its own types.

deployer/generic
deployer/task
dataflow/source
dataflow/sink
dataflow/processor

This might make it easier for component using these to understand from where the type originates.

Thought trouble with this is that existing commands only knows about raw type name.