Add os_database_connection function

The os_database_connection function is an helper used to build
database connection URI from various parameters.

Example:

  os_database_connection({
    dialect  => 'mysql',
    host     => '127.0.0.1',
    port     => '3306',
    username => 'guest',
    password => 's3cr3t',
    database => 'test',
    charset  => 'utf-8'
  })

Result:

  mysql://guest:s3cr3t@127.0.0.1:3306/test?charset=utf-8

Change-Id: Id0bde33891112e36f13d3f8fdf0ff89820c09c01
Merge "Add os_database_connection function"