describe: provide more tag info

[cwsmith]

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’

[Angelyr]

I can start this soon.

[Angelyr]

I have the tool ready, but I need a clarification on printing number of entities:

1. Should I use std::cin for the input or arguments? How would std::cin work with mpi?
2. Ask for the rank or sum all the ranks?
3. Ask for dimension or sum all the dimensions?

[cwsmith]

Great. Thank you.

1. Let's assume for now the user would run describe once just to see what fields exist and then additional times to extract field specific data (for now the number of entities with a given value). For the additional runs they would append a tag name, dimension, and value to the command line arguments.
2. Sum across all ranks. We should only count 'owned' entities with the specified value.
3. Good question. The dimension should also be provided by the user on the command line.