Modeling update

[stefanorosanelli]

In this PR some changes have been introduced in modeling module:

• object types can now be created, modified and removed
• new custom properties can be created
• relations can be created, modified and removed - also related types can be changed

Todo:

• custom properties removal
• handle hidden properties via UI (you can edit the hidden JSON attribute manually for now)
• general UI/UX improvements

[codecov]

Codecov Report

Merging #800 (5f425eb) into master (75c61b1) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #800      +/-   ##
============================================
+ Coverage     99.51%   99.52%   +0.01%     
- Complexity      928      941      +13     
============================================
  Files            72       72              
  Lines          3083     3150      +67     
============================================
+ Hits           3068     3135      +67     
  Misses           15       15              

Impacted Files	Coverage Δ
src/View/Helper/PropertyHelper.php	100.00% <ø> (ø)
src/Controller/DashboardController.php	100.00% <100.00%> (ø)
src/Controller/Model/ModelBaseController.php	100.00% <100.00%> (ø)
src/Controller/Model/ObjectTypesController.php	97.50% <100.00%> (+1.66%)	⬆️
src/Controller/Model/RelationsController.php	100.00% <100.00%> (ø)

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