Merged PR 162: Implement symbols and other stuff (see desc)

Implement symbols
- Add, Remove, Select Container
- Form
- Link with container
- Symbol behavior application to container (move to x with xpositionreference)

Important changes
- Remove SelectedContainer from HistoryState, meaning that it will be slower for each load but will be faster for each operations* (SetHistory, SelectContainer, DeleteContainer, SymbolOperations)
- ElementsSidebar now opens with isSidebarOpen meaning that both sidebar will open on toggle
- Moved camelize, transformX, restoreX to different modules (stringtools.ts, svg.ts)

src/Interfaces/IAvailableSymbol.ts

@@ -5,8 +5,8 @@ import { IImage } from './IImage';
  * Model of available symbol to configure the application */
 export interface IAvailableSymbol {
   Name: string
-  XPositionReference: XPositionReference
   Image: IImage
-  Width: number
-  Height: number
+  Width?: number
+  Height?: number
+  XPositionReference?: XPositionReference
 }