Support service initialization (boot method)

[LoicPoullain]

Issue

Resolves #628

Solution and steps

• Add ServiceManager.boot (no parameters) to init all services with a boot method.
• Allow to optionally boot services injected manually.
• Add an optional parameter to ServiceManager.boot to init only one specific service.

Checklist

• Add/update/check docs (code comments and docs/ folder).
• Add/update/check tests.
• Update/check the cli generators.

[codecov]

Codecov Report

Merging #678 into v1-8-0 will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           v1-8-0     #678   +/-   ##
=======================================
  Coverage   99.64%   99.65%           
=======================================
  Files          94       94           
  Lines        1700     1715   +15     
  Branches      399      403    +4     
=======================================
+ Hits         1694     1709   +15     
  Misses          6        6           

Impacted Files	Coverage Δ
packages/core/src/core/service-manager.ts	100.00% <100.00%> (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 ba3eaef...4cc0468. Read the comment docs.