Basic odbc connection support for MSSQL

Supports driver named driver: mssql

---
geckoboard_api_key: ''
database:
 driver: mssql
 host: localhost
 username: sa
 password: xxxx
 name: testdb
 tls_config: (optional)
  ca_file: "path/cert.pem"
  ssl_mode: "true"
refresh_time_sec: 10
datasets:
 - name: 'builds.count'
   update_type: replace
   sql: SELECT count(*) from builds
   fields:
     - type: number
       name: count