Extension Management

[korgon]

Add a new command for extension.

Sub-commands: install, update

install : command accepts name of extension (eg. chrome) and 'installs' it - where 'install' means to clone the extension repo into ~/.searchspring/extensions/<reponame>

update : command accepts name of extension and runs git pull on local extension repo

• create mapping for extensions (name -> repository details) so that any future extensions can easily be installed / updated
• handle case where not provided at all (use inquisitor and mapping made above to inquire)
• handle case where provided for not found

If possible it would be nice if we could either:

1. somehow automate chrome extension installation / configuration (may not be possible to turn on developer mode, etc...)
2. provide instructions on what buttons to press in chrome (developer mode, etc...), then open chrome to extension settings (for manual button pressing): chrome://extensions/