added linking against libmagic
Column: added non-const version of get_handler and a default ctor
Type_factory: added methods for handling mime types (libmagic)

We have a little memory leak though:

(excerpt from Valgrind)

...
==8324== 40 bytes in 1 blocks are definitely lost in loss record 2 of 3
==8324==    at 0x4C2B514: calloc (vg_replace_malloc.c:593)
==8324==    by 0x54683D0: ??? (in
/usr/lib/x86_64-linux-gnu/libmagic.so.1.0.0)
==8324==    by 0x52577F3: hawk::Type_factory::Magic_guard::Magic_guard()
(TypeFactory.cpp:32)
==8324==    by 0x52578FB: hawk::Type_factory::Type_factory()
(TypeFactory.cpp:41)
==8324==    by 0x4028F5: main (main.cpp:19)
==8324==
==8324== 40 bytes in 1 blocks are definitely lost in loss record 3 of 3
==8324==    at 0x4C2B514: calloc (vg_replace_malloc.c:593)
==8324==    by 0x5467989: ??? (in
/usr/lib/x86_64-linux-gnu/libmagic.so.1.0.0)
==8324==    by 0x5468646: ??? (in
/usr/lib/x86_64-linux-gnu/libmagic.so.1.0.0)
==8324==    by 0x52577F3: hawk::Type_factory::Magic_guard::Magic_guard()
(TypeFactory.cpp:32)
==8324==    by 0x52578FB: hawk::Type_factory::Type_factory()
(TypeFactory.cpp:41)
==8324==    by 0x4028F5: main (main.cpp:19)
==8324==
==8324== LEAK SUMMARY:
==8324==    definitely lost: 80 bytes in 2 blocks
==8324==    indirectly lost: 0 bytes in 2 blocks
==8324==      possibly lost: 0 bytes in 0 blocks
==8324==    still reachable: 0 bytes in 0 blocks
==8324==         suppressed: 0 bytes in 0 blocks

which points to somewhere in libmagic...
added an extern get_handler_hash<> header
let's get rid of this
List_dir: added 3 methods

* get_cursor, set_cursor, change_directory
Tab: directory switching, column management

Tabs are now capable of directory switching and proper column
management.