Refactor DataVisualizer and MissingDataVisualizer to enable the missing values visualizers to be converted to feature visualizers

[pdamodaran]

Describe the issue
The missing values visualizers are currently under the contrib module. Enhancements have been made to the missing values bar visualizer to be more robust to handle multiple data types. It would be ideal add these two visualizers to the list of Feature Visualizers. More details here:

In order to achieve this, the DataVisualizer and the MissingDataVisualizer need to be refactored. There might be other enhancements that need to be made to the two visualizers also.