Add Pancreas Seg app, multi-model app, and Jupyter Notebook tutorial

[MMelQin]

In this PR,

• new Pancreas Seg app is added for the Pancreas Seg model bundle published in the Model Zoo. Please note that this new app is identical to the Spleen Seg App, except for the change of name from Spleen to Pancreas in a half dozen places. The App could well have been parameterized, on the model only, for a set of segmentation model bundles in the Model Zoo, but, there has been a request to build an app for each of the few named bundles.
• add a new app to demonstrate how to support multiple models in the same app. It is more about model file organization and how to access the named model within the application than showing how a model's output can be used as the input to the next model in a ensemble, e.g. Seg model output used as input to Classification. This is because there have not been such bundles in the Model Zoo. There are already use cases for this in clinical research, and this app will help the deploy app developer.
• add the Jupyter tutorial for the multi model application. Note the use of the 22.08 version of the Nvidia PyTorch container image to avoid a torch runtime compatibility issue. A separate PR has been raised to test app compatibility and hence set the default base image to the latest Nvidia PyTorch container image.
• minor wording change in the Spleen Seg Jupyter notebook

Note: the SonarCloud reported failure is on code duplication, as noted in Item 1 above.

Signed-off-by: mmelqin mingmelvinq@nvidia.com

[MMelQin]

SonarCloud Code Analysis is false positive and complains about code duplication, 19%, for no reason.

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
18.3% Duplication

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
28.6% Duplication

[dbericat]

LGTM