Support for set of properties file

[angelozerr]

Today completion, validation, definition works inside a given properties file but it should take care of another outside properties file.

Completion sample:

• In .env file:

BDUSER=sa

• In microprofile-config.properties when completion is processed we should see DBUSER

Definition sample:

• In .env file:

BDUSER=sa

• In microprofile-config.properties when definition is processed for DBUSER

  DBUSER = sb

it should open .env and select DBUSER.

Validation sample:

• In micoroprofile-config.properties file:

quarkus.application.name=A

• In application.properties file:

quarkus.application.name=B

we should have a duplicate properties OR better having a diagnostic in quarkus.application.name inside microprofile-config.properties with DiagnosticTag.Deprecated to explain that the property is overriden by application.properties.

[angelozerr]

When Set of properties files will be implemented, it will open the door to fix https://github.com/redhat-developer/vscode-quarkus/issues/192