Non-interactive `fastdl` and `mods-install`

## User Story

As a server admin, I want a non-interactive way to install mods and build a fastdl directory so that I can automate installations.

## Basic info

* Distro: [Ubuntu 18.04]
* Game: [CS:GO]
* Command: [fastdl, mods-install]

## Further Information

There is already a command for non-interactive installations, `auto-install`. If this could be extended to the `fastdl` and `mods-install` I can automate plugin installations a bit better.

For fastdl:

`./csgoserver fastdl -f`

and for `mods-install`:

`./csgoserver mods-install sourcemod`

## Further Reading