Linux: Use config file for gateway settings (#1061)

- The following settings can be use on the config file:
  - verbose=[debug,info,notice,warn,err] - Logging verbosity.
  - log_file[0|1] - Enable logging to a file.
  - log_filepath=(FILE) - Log file path.
  - log_pipe=[0|1] - Enable logging to a named pipe(aka fifo).
    Use this option to view your gateway's log messages from the
    log_pipe_file (defined below).
    To do so, run the following command on another terminal:
    - $ cat "log_pipe_file"
  - log_pipe_file=(FILE)
  - syslog=[0|1] - Enable logging to syslog.
  - eeprom_file=[/etc/mysensors.eeprom]
  - eeprom_size=[1024]
- Change some mysgw parameters:
  - Added:
    - -q, --quiet:  for quiet mode, disable log messages written to the
    terminal.
  - Removed:
    - -d, --debug: removed, log messages are now enabled by default.
  - Replaced:
    - -b, --background: replaced by --daemon
- isatty() is no longer used, log messages by default are printed to
  stderr unless the gateway is started with --quiet (#1022)
- MY_LINUX_CONFIG_FILE: no longer holds the path to the eeprom file,
  but to the configuration file

drivers/Linux/config.h

@@ -0,0 +1,45 @@
+/*
+ * The MySensors Arduino library handles the wireless radio link and protocol
+ * between your home built sensors/actuators and HA controller of choice.
+ * The sensors forms a self healing radio network with optional repeaters. Each
+ * repeater and gateway builds a routing tables in EEPROM which keeps track of the
+ * network topology allowing messages to be routed to nodes.
+ *
+ * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
+ * Copyright (C) 2013-2018 Sensnology AB
+ * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
+ *
+ * Documentation: http://www.mysensors.org
+ * Support Forum: http://forum.mysensors.org
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct config {
+	int verbose;
+	int log_file;
+	char *log_filepath;
+	int log_pipe;
+	char *log_pipe_file;
+	int syslog;
+	char *eeprom_file;
+	int eeprom_size;
+} conf;
+
+int config_parse(const char *config_file);
+void config_cleanup(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif