Resolve two loading spinners when loading platforms

Closes #397 (closed)

The loading spinner issue has been solved by adding the two private properties for PlatformSearch component. I guess, the cause is that we used isLoading private property in both fetch(), runSearch() method for initial data and performing search operations. That may be produce two loading spinner issue.

The showSpinner getter returns true, if either isLoading or isFetchingResults is true, which can be used to conditionally display a loading spinner.