Merged PR 167: Add Flex and fix bugs (read desc)

Note: The branch name does not fit the new features.

- Implement Flex with simplex
- Enable rigid body by default (removed IsRigidBody property) <=== possibly a bad idea
- Sort children in add and update properties
- Implement MaxWidth
- Add more docs

Fixes :
- .env.production url
- Symbols: not blocking the linked container when the parent is moving

src/Interfaces/IAvailableContainer.ts

@@ -1,6 +1,7 @@
 import React from 'react';
 import { AddMethod } from '../Enums/AddMethod';
 import { XPositionReference } from '../Enums/XPositionReference';
+import { IMargin } from './IMargin';
 
 /** Model of available container used in application configuration */
 export interface IAvailableContainer {
@@ -10,6 +11,9 @@ export interface IAvailableContainer {
   Width?: number
   Height?: number
   MinWidth?: number
+  MaxWidth?: number
+  Margin?: IMargin
+  IsFlex?: boolean
   AddMethod?: AddMethod
   XPositionReference?: XPositionReference
   CustomSVG?: string