Add Linux repositories

To install wallet with somethink like: sudo apt-get install raiblocks-core

[rkeene]

We should support CentOS/RHEL 7, Ubuntu LTS, and Debian with our repositories. These should mirror the artifacts we produce for Docker.

[rkeene]

To start with, and to satisfy #1091 we should create a CentOS 7 repo first and support V15.2 on it.

systemd unit files and packaging guides for rai_node already exist that we can adopt.

[argakiig]

V16.0 will have a RPM package for RHEL systemd systems.
A new user nanocurrency is created with a home directory of /var/nanocurrency
Daemon will be installed to /usr/bin and a unit file for nanocurrency will be installed but not enabled or started.
More information as things progress

[argakiig]

• Source tarball
• RPM build
• DEB build
• Repositories created.
• Automation of package creation