Add cache and pull to refresh options

[alexrintt]

When the app is relaunched, the list is refreshed again.

Add following options:

• Cache results (disabled by default).
  • Store applications metatada in the local storage, so in the next startup the app list is pulled from storage instead of fetching from OS.
• Manual refresh (disabled by default).
  • If enabled the list will never be refreshed if cache is available. A manual pull to refresh on homepage (or settings maybe) is required to refresh app list. If disabled, the app list will be loaded in background everytime the app starts.