GUI - Enable "brandability" of the MetaPack GUI client

[SubPointSupport]

MetaPack GUI client should support "brandability" scenario so that it can be used as "my product installer". The following scope is to be considered:

• configuration to enable/disable metapack gui tabs
• configuration to inject your own custom landing page (start page control)
• configuration to setup default NuGet Galleries with your packages
• ability to create a ZIP package our of pre-configured MetaPack GUI client