Merged PR 179: Fix bugs about flex and context menu (see desc) + disable hard rigid behavior + add missing properties to form + Clean up css

- Clean up some css class
- Fix wrong order when applying flex
- Fix Replace behavior not working because previous container was still existing
- Disable hard rigid behavior which disallow two container to overlap
- Add ENABLE_FLEX, ENABLE_HARD_RIGID ENABLE_SWAP
- Add missing form properties with dimensions
- Update readme

test-server/http.js

@@ -55,6 +55,7 @@ const GetSVGLayoutConfiguration = () => {
         Type: 'Chassis',
         MaxWidth: 500,
         MinWidth: 200,
+        Width: 200,
         DefaultChildType: 'Trou',
         Style: {
           fillOpacity: 1,
@@ -63,7 +64,7 @@ const GetSVGLayoutConfiguration = () => {
           fill: '#d3c9b7',
         },
         ShowSelfDimensions: true,
-        IsDimensionBorrower: true
+        IsDimensionBorrower: true,
       },
       {
         Type: 'Trou',