Describe Improvements

[Angelyr]

Related to this issue: #77 (comment)

In the describe tool, we should add the following info on each tag:

• number of entities with a given values (this would require additional user input: tag name and value)
• min and max across all processes
• type (int, bool, float, real, etc.)
• change ‘size per entity’ → ‘number of components’

[cwsmith]

Looks good. A few comments are below.