Simplify auto check for updates

[hql287]

Description

This PR simplified the way Manta handle checking for updates by removing unnecessary settings and automatically check for update on startup.

Related Issue

Issue #261

Motivation and Context

• The user won't need to remember whether they should check for update or not (unless they want to) as this would be handled automatically by Manta.
• Unnecessary options such as check for updates frequency will be safely removed from the app, UI will be simplified.

How Has This Been Tested?

• On startup, Manta did run the checkForUpdate function silently (Using a simple console.log())
• If there's new update, showed a dialogue box
• If there's no update, did nothing.
• If the user check for update explicitly, always show dialogue box.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have included a migration scheme (If type of change is breaking change)