Add I/O type hinting, remove duplicate code, improve Docblock, add some optimizations

[ker0x]

This PR do:

• add input/output type hinting for methods (as the minimum PHP version is set to 7.0 in composer.json)
• remove some duplicate code already present in parent or abstract class
• improve Docblock
• add small optimizations

Warning

If this PR is merged, the next release should be tag 2.0 as it bring I/O type hinting. By doing so, this will avoid BC break for people using version < 2.0

[codecov[bot]]

Codecov Report

Merging #84 into master will decrease coverage by 0.61%. The diff coverage is 74.31%.

@@             Coverage Diff              @@
##             master      #84      +/-   ##
============================================
- Coverage     71.17%   70.55%   -0.62%     
+ Complexity      477      429      -48     
============================================
  Files            49       49              
  Lines          1332     1304      -28     
============================================
- Hits            948      920      -28     
  Misses          384      384

Impacted Files	Coverage Δ	Complexity Δ
src/Events/FacebookEvent.php	60% <ø> (ø)	2 <0> (ø)	:arrow_down:
src/Commands/Nlp.php	0% <0%> (ø)	4 <0> (ø)	:arrow_down:
src/Commands/AddPersistentMenu.php	0% <0%> (ø)	4 <0> (ø)	:arrow_down:
src/Commands/WhitelistDomains.php	0% <0%> (ø)	4 <0> (ø)	:arrow_down:
src/Commands/AddGreetingText.php	0% <0%> (ø)	4 <0> (ø)	:arrow_down:
src/Events/MessagingPostbacks.php	0% <0%> (ø)	1 <1> (ø)	:arrow_down:
src/Providers/FacebookServiceProvider.php	0% <0%> (ø)	5 <1> (ø)	:arrow_down:
src/Commands/AddStartButtonPayload.php	0% <0%> (ø)	4 <0> (ø)	:arrow_down:
src/Events/MessagingDeliveries.php	100% <100%> (ø)	1 <1> (ø)	:arrow_down:
src/Events/MessagingOptins.php	100% <100%> (ø)	1 <1> (ø)	:arrow_down:
... and 24 more

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[christophrumpel]

Hey @ker0x, thanks for the PR.

We like the docblocks on one line if possible like /** @var ... **/. The return types addition is nice, but we would want to change that in all repositories which is a lot of work. We also want to that together when we change. So I can't merge this PR now.

If you could change the docblock onliners back and remove the return types. We can merge this now and later the return types.

[ker0x]

Hello @christophrumpel,

Thank you for your feedback. I've closed this PR due to problems with my master branch and open a new one with changes that you requested (#87).