[template] && [template-build] simplify updates and workflow for regular users

[b-ma]

1. Add a dependency check with automatic install in the clean step, to simplify updates for regular users (cf. https://www.npmjs.com/package/check-dependencies)

2. Add an update script to hide git pull origin master behind npm run update. Probably making it work with master branch should be enough for most use-cases. Possible solutions:

   • https://www.npmjs.com/package/simple-git
   • https://www.npmjs.com/package/nodegit
   • https://www.npmjs.com/package/isomorphic-git (pure JS implementation, no build problems...)

@note: this probably require users to have a github account (maybe check that: https://superuser.com/questions/557903/clone-github-repository-without-account, will need a machine without git, github account nor SSH key to be tested)

3. Option: add START.command and START_DEV.command scripts