install default collections

[mmetc]

As soon as possible after the package is installed (possibly before running crowdsec) we need to install the pfsense collection, which is currently in a branch of the hub. So the procedure is:

• if the file /usr/local/etc/crowdsec/collections/pfsense.yaml already exists: ignore all the following steps
• set "cscli.hub_branch: pfsense-gui" in config.yaml
• cscli hub update
• cscli collections install crowdsecurity/pfsense
• service crowdsec reload

This can be executed, for example, when the settings form is saved and we ensured that crowdsec is running

[julienloizelet]

Should be done here: https://github.com/crowdsecurity/pfSense-pkg-crowdsec/pull/26