Refactored startup script and configuration handling

• Removed command line option to specify the pid
• Removed command line option to specify the main configuration file
• Added a command line option to specify the configuration directory
• Added a command line option to specify the runtime directory
• The main configuration file name is now immutable (config.ini)
• The pid file name is immutable (sylk-server.pid)
• All configuration files are now treated consistently
• Properly read both local and system wide configurations
• Do not initialize the runtime directory when not forking