New Partition type jobs

Hello,

This MR creates two jobs to set the partition type, one for GPT and one after the file-system is created.

The first commit creates the job SetPartitionTypeJob that sets the GPT partition type, as it is done for the other GPT data (i.e. SetPartitionLabelJob, SetPartitionUUIDJob and SetPartitionAttributesJob).

Note: Maybe for the jobs should be renamed to include GPT, before the next release.

The second commit creates the job SetPartTypeJob that sets the partition system type. It is similar to the job above, but uses the method setPartitionSystemType() instead of setPartitionType() that takes no type parameter. The value is guessed by the function it self (see static function getPartitionType() and typemap).

Note: The name SetPartTypeJob instead of SetPartitionTypeJob or even SetPartitionSystemTypeJob is influenced by SetPartFlagJob that uses the method setFlag().

The third commit reuses the method setPartitionType() introduced by the first commit in the method setFlag() to factorize and simplify the code.