[CLI] StructOpt added, code reorganized

[damirka]

Motivation

Motivation for this PR has been described here: #584
Short: this not-so-big refactor builds a foundation for future extensions and improvements of CLI application.

Closes #604
Closes #599
Closes #584
Closes #277
Closes #376 (adds warning when no inputs are found)
Closes #596 (won't do)

Changelog

• wrapped everything into StructOpt
• logging and timers are defined in a single place - commands look cleaner and easier to read
• all API calls are in single place with proper error handling (no unknowns in this one) - see api code
• all of the traits and structures feature documentation which can be then built with rustdoc
• leo login <TOKEN> now works (didn't before)
• all of the scenarios in leo login work: no token, has token, param missing - everything is in place
• global params for application are now easily defined
• custom error classes replaced with inlined anyhow!(), more error handlers added
• improved error messages for verbosity and better understanding of what really happened
• integration tests added, use cargo test to use
• added --quiet or -q option to suppress output
• adds -f flag to leo test to test specific file(s)

Test Plan

Integration tests for CLI are included

[codecov]

Codecov Report

Merging #618 (56ec74d) into master (770f660) will decrease coverage by 0.73%.
The diff coverage is 78.66%.

@@            Coverage Diff             @@
##           master     #618      +/-   ##
==========================================
- Coverage   75.63%   74.89%   -0.74%     
==========================================
  Files         518      548      +30     
  Lines       16135    17245    +1110     
==========================================
+ Hits        12204    12916     +712     
- Misses       3931     4329     +398     

Impacted Files	Coverage Δ
leo/lib.rs	100.00% <ø> (ø)
leo/main.rs	100.00% <ø> (ø)
leo/commands/package/login.rs	52.94% <52.94%> (ø)
leo/api.rs	62.16% <62.16%> (ø)
leo/commands/update.rs	77.77% <75.00%> (ø)
leo/commands/test.rs	74.07% <75.60%> (ø)
leo/commands/build.rs	75.67% <80.00%> (ø)
leo/commands/setup.rs	52.94% <84.61%> (ø)
leo/context.rs	87.50% <87.50%> (ø)
leo/commands/prove.rs	100.00% <100.00%> (ø)
... and 88 more

---

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 770f660...5a031d1. Read the comment docs.

[howardwu]

I'd like add, remove, login, logout, and publish without package keyword.

[damirka]

@howardwu updated PR. Ready for review again.

[damirka]

Also fixes #376 - added note in PR description above.

When testing library without inputs user receives a warning that no inputs were found:

  Test Unable to find inputs, ignore this message or put them into /inputs folder
  Test Running 1 tests
  ...

[damirka]

Reopened as #632 for CI support.