suggestion:provider option installer and skipInstallSilent

[bung87]

https://github.com/yeoman/generator/blob/9daf15e487d5062aac81fa2a8c138911baffb9d7/lib/actions/install.js#L26

install.scheduleInstallTask = function(installer, paths, options, spawnOptions) { 

1. the reason for provider option installer: current use this.npmInstall when this project use as composeWith with other generator may conflict with its option, assuming the generator ask end user chose a package manager.

2. the reason for provider option skipInstallSilent: this may contains in yeoman/generator project , when I use this project with composeWith set skipInstall false, during generate new project I got "Skipping install command: npm install --cache-min 86400" 2 times, therefore I use yarnInstall in my generator install method. better let other generator author decide when to install.