SSR: Optionally disable bundling of server

[th3l0g4n]

Is your feature request related to a problem? Please describe.
With version 1.5.0 of @quasar/app, bundling of the Node Server Part (when using SSR) was introduced.
Unfortunately this might lead to unexpected behaviour regarding env var injection and FS path resolution.
There is currently no option to disable this feature so that the SSR Version of @quasar/app 1.5.X behaves the same way (just copying server file and extensions) like the previous versions.

In my opinion there is also no real benefit of processing the server parts with webpack, as you have complete control over the execution environment.

Describe the solution you'd like
Add a Flag in the quasar.conf to completely disable bundling of the server.