Schema popup on Add/Edit dialogs

## Background
Currently, choosing a Schema for a Mapping Table or a Dataset in the Add/Edit dialog gives you the option to choose the Schema's name and version. If you aren't sure which version you want to use, you have to open a separate tab and double check.

## Feature
We can have a button which opens a popup schema browser, which allows you to double-check the schema being selected is the correct one.

## Proposed Solution [Optional]
Solution Ideas
1. Place a button next to the schema select
2. On select - fetch the schema and display in a popup table