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/Components/Editor/Behaviors/SymbolBehaviors.ts

@@ -0,0 +1,9 @@
+import { IContainerModel } from '../../../Interfaces/IContainerModel';
+import { ISymbolModel } from '../../../Interfaces/ISymbolModel';
+import { restoreX, transformX } from '../../../utils/svg';
+
+export function ApplySymbol(container: IContainerModel, symbol: ISymbolModel): IContainerModel {
+  container.properties.x = transformX(symbol.x, symbol.width, symbol.config.XPositionReference);
+  container.properties.x = restoreX(container.properties.x, container.properties.width, container.properties.XPositionReference);
+  return container;
+}