[Enhancement] Popup display in model and segment app

[amritansh22]

Description

In model app:

• After changing class list, instead of an alert a popup is shown.
• UI of class change button

In segment app

• After uploading model, a popup is shown.
• After deleting model, instead of an alert a popup is shown.

Motivation and Context

Improves User Interface

How Has This Been Tested?

Tested in Chrome and Firefox

Screenshots (if appropriate):

Types of changes

**What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

**Go over all the following points, and put an x in all the boxes that apply.
**(If you're unsure about any of these, don't hesitate to ask. We're here to help!)

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[birm]

I'm still getting an alert on model.html on changing classes. Have I missed/misunderstood something?

[amritansh22]

@birm I had missed that. Sorry about it.

[birm]

Thanks for the improvement!!