Update time output for block get

[sukantoraymond]

Closes #433

This PR outputs additional unix format for timestamp and renames "timestamp" to "proposal timestamp"

---

For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[sukantoraymond]

I don't see the reason why we have to make the timestamp consistent. Thoughts? @sideninja #433

[sukantoraymond]

Sample output