gRPC extended Demos

[juanpedromoreno]

This PR brings new examples trying to show the different scenarios explained in the gRPC Concepts docs.

[codecov-io]

Codecov Report

Merging #6 into master will not change coverage.
The diff coverage is 0%.

@@         Coverage Diff          @@
##           master    #6   +/-   ##
====================================
  Coverage       0%    0%           
====================================
  Files           5     6    +1     
  Lines          26   102   +76     
  Branches        0     3    +3     
====================================
- Misses         26   102   +76

Impacted Files	Coverage Δ
demo/src/main/scala/GreetingService.scala	0% <0%> (ø)	⬆️
demo/src/main/scala/GreetingClientApp.scala	0% <0%> (ø)	⬆️
demo/src/main/scala/GreetingClient.scala	0% <0%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bebcb65...1f9f9f7. Read the comment docs.