Plugin enhancements to streamline user onboarding

[guofoo]

• Currently the plugin cannot be found by name (Sketch2App or AppChef) from Sketchapp's offical plugin directly
• Remove requirement to download Sketchpacks in order to install plugin
• Rename plugin to AppChef or AppChef Instant Plugin for easy searchability
• Add Direct plugin-install inks to help and document pages
• When uploading, try not to make block the entire Sketch UI; try to run process in background
• Provide a upload Progress Bar to indicate how long it will take

[guofoo]

• Install Sketchtool menu item, is it required?
• Tried it and it failed on systems that already has it installed, need to change message
• Perhaps provide auto install script to install it through command line as part of a "master script" for installation and setup of environment

[guofoo]

• Add a "Help" or "Get Started" menu option in the plugin dropdown - provide information on what users can/should do to get started using the system