Support external files altogether with the yaml file

[lordrip]

Please describe the feature that you want to propose

Support external files altogether with the yaml file, for instance, schema files, XSLT supporting files, properties files, etc...

[igarashitm]

There're 2 categories:

1. The ones that going to be a part of deployment (properties file, XSLT file for camel-xslt step, etc)
2. The other is a design time only files (schema files which camel component is not aware, used for data mapper UI)

[kahboom]

Some questions:

• Where will these files live? Will it be based on their environment (i.e. as a custom resource, in some directory) or an external store (GitHub, AWS, etc.)?
• Similarly, will the backend only be aware of deployment-related files or design-time files as well? In other words, will these files be retrieved from/passed to the backend regularly?
• Are these files intended to be modified?
• What kind of services do these files need? For example are we intending to validate these files somehow?

Depending on the answer to those questions, it might make sense to mark this as an epic and break it up into separate tasks.