lib: Move space command classes into a distinct translation unit.

This affects the following classes:
* SpaceCommandFormatException
* MissingCommandParameterException
* IllegalCommandParameterException
* SpaceCommand
* SpaceCommandSerializer
* TextSpaceCommandSerializer
lib: Introduce a util translation unit for utility classes and methods.
lib: added hex2int from i2cmethods to utilities.
lib: added int2hex from i2cmethods to utilities.
lib: restructured util/int2hex

use a distinct function to calculate the hex width
lib: added retrieveHexParameter from i2cmethods to utilities.
I3C Client: Use xmppsc/util.h for utility methods
I3C CLI: Use xmppsc/util.h for utility methods
I3C CLI: Removed i3c_client dependency.
Merge pull request #32 from penguineer/restructure

Restructuring which mainly leads to a better decoupling of software components.
(I3C CLI no longer depends on I3C Client)
I3C_CLI: Extracted the classes FinalizingCommandMethod and I3CResponseMethod for sharing.
Merge pull request #33 from penguineer/master

I3C_CLI: Extracted the classes FinalizingCommandMethod and I3CResponseMe...
Method handler: Added an assertion fail for the cerr output

In Debug mode the dispatcher fails when no method has been found and the map did not throw an exception. In theory this should never happen.
I3C Client: In daemon mode: print errors to syslog.
I3C Client: Really exit on SIGHUP.
[REVIEW] Daemon: Storing PIDs is always successful when no path given.

This follows the logic of having no PID file when there is no PID path, i.e.
the PID is virtually stored in the sense that storing did not fail.