Add new `Selector` app structure

[thomaseleff]

Currently, the selector parameter for assemblit pages requires a Setting app-structure to be passed as the value. However, the Setting app-structure requires a number of additional parameters that are not required for the selector to be built.

To Do:

• Create a new app-structure for selector component
• Implement the new app-structure within all assemblit pages that require a selector component
• Test and resolve all bug issues related to implementing the new app-structure

[thomaseleff]

A Selector object requires the following attributes,

• parameter
• name optional
• description optional