plugin architecture: dashboards/visualizations

[mmguero]

This is a sub-issue of Malcolm "plugin architecture" #399

Probably the simplest kind of plugin is adding a new visualization or dashboard to OpenSearch dashboards. Code needed for this might include:

• the plugin archive would contain JSON files representing OpenSearch saved objects for OpenSearch dashboards
• the code that loads the dashboards in would need to do some kind of sanitation
  • essentially, the search-and-replace discussed here for the following in case they forgot to do it when they generated it
    • MALCOLM_NETWORK_INDEX_PATTERN_REPLACER
    • MALCOLM_OTHER_INDEX_PATTERN_REPLACER
    • MALCOLM_NETWORK_INDEX_TIME_FIELD_REPLACER
    • MALCOLM_OTHER_INDEX_TIME_FIELD_REPLACER
  • this could probably be done here prior to expanding the replacers to their final values
• Some sort of code that could cause these to be automatically added to the left navigation pane of the normal Malcolm dashboards?