Deploy Alkane on webserver-alkane role

Summary:
Deploy and configure the Alkane utility. Alkane is built as FreeBSD
port and package to serve through the Nasqueron packages repository.

It runs under the user deploy so it has rights to modify the sites files.

Ref T1826.
Ref T1828.

Test Plan: Deploy on Windriver and test deployment to dummy sites

Reviewers: dereckson

Maniphest Tasks: T1828, T1826

Differential Revision: https://devcentral.nasqueron.org/D3013