Migrating existing documentation for the sample

[plavjanik]

Resolves #8, resolves #22, and resolves #33

The documentation that is listed in #8 has been reviewed and migrated to the sample where it was possible.

Please review the new documentation if it makes sense and is helpful to you.

The message format class from the common-service-code were migrated as well under new package name with prefix org.zowe.commons.error. This code has been already review when developed by @JirkaAichler and Vasyl so you do not need to spend much time on this but your comments will be appreciated.

[codecov-io]

Codecov Report

Merging #36 into master will increase coverage by 0.48%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master      #36      +/-   ##
============================================
+ Coverage     78.19%   78.67%   +0.48%     
- Complexity       46       47       +1     
============================================
  Files            21       22       +1     
  Lines           133      136       +3     
  Branches          3        3              
============================================
+ Hits            104      107       +3     
  Misses           27       27              
  Partials          2        2

Impacted Files	Coverage Δ	Complexity Δ
...we/sample/apiservice/config/ApplicationConfig.java	100% <ø> (ø)	3 <0> (ø)	⬇️
.../org/zowe/sample/apiservice/wto/WtoController.java	100% <ø> (ø)	2 <0> (ø)	⬇️
...e/greeting/GreetingControllerExceptionHandler.java	100% <100%> (ø)	2 <2> (?)
...owe/sample/apiservice/greeting/EmptyNameError.java	100% <100%> (ø)	1 <1> (?)
...sample/apiservice/greeting/GreetingController.java	100% <100%> (ø)	4 <2> (?)
...we/sample/apiservice/config/WebSecurityConfig.java	100% <100%> (ø)	3 <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 ed85421...0e9836b. Read the comment docs.

[plavjanik]

Fixed problems discovered by Dan:

• Missing WWW-Authenticate header on 401 when no authentication has been provided
• No error where .so was not build prior packaging JAR

[VitekVlcek-Broadcom]

Me and Petr reviewed this PR.