transport: move files to a subdirectory in preparation of a split

In prepraration of splitting all LogTransport classes into separate
files, this patch moves all base files to the newly created subdirectory,
and patches Makefiles to make these compile properly from the new location.

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: extract LogTransportFile to a separate module

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: extract LogTransportPipe to a separate module

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: extract LogTransportDevice to a separate module

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: extract LogTransportSocket to a separate module

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: remove unneeded headers from logtransport.c

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: update copyright notice

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
transport: rename tlstransport to transport-tls

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>