Add a mongo db application stack.

[metlos]

What does this PR do?

Adds a stack with nodejs and mongodb with an example application.

Current problems:

• the application started through the command seems to stop after a couple of minutes (this seems to be an issue with Che or even K8s in general?)
• The example curl command to create a user is stuck and generates no response. I didn't find the root cause for this yet.

What issues does this PR fix or reference?

eclipse-che/che#13529

[l0rd]

the application started through the command seems to stop after a couple of minutes (this seems to be an issue with Che or even K8s in general?)

maybe related to #13620?

[metlos]

the application started through the command seems to stop after a couple of minutes (this seems to be an issue with Che or even K8s in general?)

This is caused by eclipse-che/che#13620 and so can be dealt with separately.

The example curl command to create a user is stuck and generates no response. I didn't find the root cause for this yet.

This was caused by eclipse-che/che#8134 and thus was an issue with my local setup.

So this PR is ready for review I think.