Allow for client-side routing, set up `/access-denied` (#48, #209)

[ssciolla]

The PR aims to resolve #48 and #209. This is somewhat experimental, but I believe it works well. I think it could help us handle some other issues, such as #253 and #312. It also is related to the closed issue #103.

Note(s):

• Switches from app.useStaticAssets to using ServeStaticModule, which is designed for single-page-applications.
• Because ServeStaticModule is now registered in app.module.ts, helmet and its Content Security Policy (CSP) settings now apply to the static assets served. This is likely a good thing, but means we need to do more CSP configuration (included here). Without them, the iframe was getting blocked in the Canvas test instance.
• Adds a higher-level instance of Switch in client/index.tsx, so we can have public routes for error messages and redirect effectively to them from the server and client (see changes to lti.service.ts and App.tsx).

[pushyamig]

@ssciolla one thing I noticed is when you open CCM in it's own window and try some random URL, it not show access denied page, instead react code is loading and i see some error with Breadcrumbs missing data. I feel other than the routes described in the FeatureUIData.tsx should be routed to default no-page found

[pushyamig]

May Be in the code below you might need add a default route?

<Breadcrumbs {...{ features, pathnames }} />
      <Switch>
        <Route exact={true} path='/'>
          <Home globals={globals} course={course} setCourse={setCourse} getCourseError={getCourseError} />
        </Route>
        {features.map(feature => {
          return (
            <Route key={feature.data.id} path={feature.route}>
              <feature.component
                globals={globals}
                course={course}
                title={feature.data.title}
                helpURLEnding={feature.data.helpURLEnding}
              />
            </Route>
          )
        })}
        <Route><div><em>Under Construction</em></div></Route>
      </Switch>

[ssciolla]

May Be in the code below you might need add a default route?

@pushyamig, nice catch! This is a bug, there are stack traces related to Breadcrumbs working on it now. I'll also add a "nothing here" page.

[ssciolla]

@pushyamig, okay, this should be fixed. Please test again.