doc/mi.md: update document

doc/mi.md: update document

Major differences:

  * The document has a version
  * New Definitions section
  * Clarify the roles of the analysis and the consumer
  * Describe input format arguments more formally
  * Specify the exit status of the analysis as part of
    the output format
  * Add progress indication (with --output-progress
    argument) feature
  * New Common objects section
  * New Error object section: an error object can be
    written by the analysis during both the metadata
    and analysis phases
  * Add mandatory `class` property in the properties
    table of the individual data object sections
  * Style fixes

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>