Angular 2 multiple modules

Two things need to be done here:

First, export TopNavigation & Search components from the CommonModule so they can be used in other modules:

// Common module - common.module.ts
import { NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { BrowserModule }  from '@angular/platform-browser';
import { TopNavigation } from './components/header.component';
import { Search } from './components/search.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ TopNavigation, Search ],
  exports: [ TopNavigation, Search ],
  schemas: [ CUSTOM_ELEMENTS_SCHEMA ]
})
export class CommonModule {}

Secondly, the CommonModule should be imported by the Module that actually uses it. In your case the SpreadSheet module should import CommonModule

// Spreadsheet module - spreadsheet.module.ts
import { NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { BrowserModule }  from '@angular/platform-browser';
import { Spreadsheet } from './components/spreadsheet.component';
import { CommonModule } from './common/common.module';

@NgModule({
  imports: [ BrowserModule, CommonModule],
  declarations: [ Spreadsheet ],
  schemas: [ CUSTOM_ELEMENTS_SCHEMA ]
})
export class SpreadsheetModule { }

Modules do not inherit components are declared in other modules. So when you import CommonModule in AppModule it does not have any effect.

You can read here for more info.