Improve size and speed of plugin installation

[amandel]

Is your feature request related to a problem? Please describe

Currently the installation of plugins does a full clone of the plugin repo. For java this pulls 355MB over the network while only ~22MB are really needed, This uses time, bandwidth and hdd space.

Describe the proposed solution

Adding "--depth 1" to the git clone call in git.go should directly speed this up and reduce hdd usage.

Describe similar asdf features and why they are not sufficient

Describe other workarounds you've considered