Refactor build system to remove sub-library dependencies

Scheduler/Console: Add 'sys' directory
Scheduler: Implement EventManager and 'sys/scheduler/events' command

Scheduler: Move remaining non-public implementation classes into 'detail' namespace
Adjust rest of SENF accordingly

Scheduler: Clean up FIFORunner::TaskInfo interface
Update rest of senf to use the new API

Scheduler: Add automatic periodic resync to ClockService::abstime() and ClockService::clock()
Scheduler: Add task nameing
Scheduler: BUGFIX: Add missing task-dequeue in FdDispatcher::add()
Scheduler: Add empty() member to all dispatchers
Scheduler: Add eventTime() support to FdManager
Scheduler: Add support for non-pollable file descriptor detection to FdManager and FdDispatcher
Scheduler: Add FIFORunner task watchdog
Scheduler: Add debugging backtrace to FIFORunner
Scheduler: Change senf::Scheduler implementation to use the new dispatcher infrastructure
Scheduler: BUGFIX: Fix access to (possibly) destroyed object in TimerEvent::run()
Utils: Add senf::signalName() helper
Utils/Daemon: Use senf::signalName() in debug messages
Utils/Logger: Fix logger to correctly format the timestamp (the deadlock should be fixed now)
Update scheduler callback signatures to the new API throughout the project
Update documentation

Console: Rewrite parser semantic actions to use phoenix (much (cd ..) simpler ...)

Console: Implement (and document) Server::stop()
Console: Implement working readline C-d and minnimal C-c support
Utils/Logger: Make Stream optional in routing commands

Console: Remove backtrace from syntax error messages
Console: auto-cd when specifying a directory as command