CakePHP 4 compatibility

[Erwane]

CakePHP4 with Bootstrap 4

• DateTimeWidget was removed. Default CakePHP4 use Html5 datetime input now.
• Code syntax was fixed with "PHP CodeSniffer" and CakePHP CodeSniffer standard.
• Licence was updated in each files.
• Tests was fixed.
• Travis was upped to php7.2 and cake 4
• composer requirements was updated.

warning : should define a branch name to reflect the cake and bs versions.

[codecov[bot]]

Codecov Report

Merging #191 into v4.0.3 will decrease coverage by 1.62%. The diff coverage is 88.13%.

@@             Coverage Diff              @@
##             v4.0.3     #191      +/-   ##
============================================
- Coverage     88.26%   86.63%   -1.63%     
  Complexity      380      380              
============================================
  Files            20       19       -1     
  Lines          1167     1190      +23     
============================================
+ Hits           1030     1031       +1     
- Misses          137      159      +22

Impacted Files	Coverage Δ	Complexity Δ
src/View/Widget/ColumnSelectBoxWidget.php	0% <0%> (-91.67%)	3 <3> (ø)
src/View/Helper/FlashHelper.php	0% <0%> (ø)	5 <5> (ø)	:arrow_down:
src/View/Helper/EasyIconTrait.php	92.59% <100%> (+0.92%)	7 <7> (-1)	:arrow_down:
src/View/Widget/LabelLegendWidget.php	100% <100%> (ø)	3 <3> (ø)	:arrow_down:
src/View/Helper/ClassTrait.php	95.12% <100%> (+0.38%)	12 <12> (ø)	:arrow_down:
src/View/Helper/UrlComparerTrait.php	98% <100%> (-2%)	27 <27> (+2)
src/View/EnhancedStringTemplate.php	95.65% <100%> (+1.2%)	8 <8> (ø)	:arrow_down:
src/View/FlexibleStringTemplate.php	93.75% <100%> (ø)	7 <7> (+1)	:arrow_up:
src/View/Widget/InlineRadioWidget.php	83.72% <100%> (+0.79%)	19 <19> (ø)	:arrow_down:
src/Utility/StackedStates.php	100% <100%> (ø)	11 <11> (ø)	:arrow_down:
... and 11 more

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[Holt59]

Merge to cake4-bs4-1.0.0, working on a cleaner versioning scheme.