Rename service[zabbix_server] to service[zabbix-server]

This is to prepare for zabbix::server_package.rb
Yum cookbook version 3.0.0 introduced breaking changes, depend on earlier versions

yum::epel doesn't exist any more, only LWRPs seem to exist. Depend on an
earlier version than 3.0.0.
Postgres cookbook is borked in 3.3.x for now, depend on 3.2.0. Use earlier yum version.

See https://github.com/hw-cookbooks/postgresql/issues/94
Use earlier yum version as well due to yum::epel not existing in version 3.0.0
of yum cookbook.
Add package support to database provider

The database packages for Zabbix install the SQL files necessary. Set
`package_install` in the arguments if using a package. The paths vary depending
on engine and version, making the `sql_path` argument necessary as well.
Added support for installing `zabbix::database` via packages.

Currently only works on Postgres.