LuaLogging: A simple API to use logging features in Lua

LuaLogging
A simple API to use logging features in Lua. Portuguese version.

## SQL appender

The SQL appender can be used to write log messages to a SQL database table. It uses LuaSQL, therefore any database supported by LuaSQL can be used.

    function logging.sql{
        connectionfactory = function,
        [tablename = string,]
        [logdatefield = string,]
        [loglevelfield = string,]
        [logmessagefield = string,]
        [keepalive = boolean],
    }

- `connectionfactory`:
  This must be a function that creates a LuaSQL connection object. This function will be called everytime a connection needs to be created.
- `tablename`:
  The name of the table to write the log requests. Default value is `"LogTable"`.
- `logdatefield`:
  The name of the field to write the date of each log request. Default value is `"LogDate"`.
- `loglevelfield`:
  The name of the field to write the level of each log request. Default value is `"LogLevel"`.
- `logmessagefield`:
  The name of the field to write the message of each log request. Default value is `"LogMessage"`.
- `keepalive`:
  In every log request a connection to the database is opened, the message is written, and the connection is closed.
  If the user wants to keep the connection opened he can specify `keepalive = true`.

## Example

    require"logging.sql"
    require"luasql.jdbc"

    local env, err = luasql.jdbc('com.mysql.jdbc.Driver')

    local logger = logging.sql {
      connectionfactory = function()
        local con, err = env:connect('jdbc:mysql://localhost/test',
                                     'tcp', '123')
        assert(con, err)
        return con
      end,
      keepalive = true,
    }

    logger:info("logging.sql test")
    logger:debug("debugging...")
    logger:error("error!")