lsfd: introduce -Q option for generic filtering

lsfd: introduce -Q option for generic filtering

Examples:

    # ./lsfd -Q "(FD <= 9) and (TYPE == 'SOCK')" -Q "COMMAND == 'ssh'" | head
    COMMAND     PID USER ASSOC MODE TYPE SOURCE MNTID    INODE NAME
    ssh      153907 root     4  rw- SOCK sockfs     9  2450021 TCP:[2450021]
    ssh     1657696 root     4  rw- SOCK sockfs     9 64357645 TCP:[64357645]
    ssh     1657696 root     5  rw- SOCK sockfs     9 64363596 UNIX:[64363596]
    ssh     2345473 root     4  rw- SOCK sockfs     9 81978848 TCP:[81978848]
    ssh     2345473 root     5  rw- SOCK sockfs     9 81980736 UNIX:[81980736]
    ssh     2345473 root     9  rw- SOCK sockfs     9 81980737 UNIX:[81980737]
    ssh     2345475 root     4  rw- SOCK sockfs     9 81975091 UNIX:[81975091]
    ssh     3958804 root     0  rw- SOCK sockfs     9 87840900 UNIX:[87840900]
    ssh     3958804 root     4  rw- SOCK sockfs     9 87836642 TCP:[87836642]

    # ./lsfd -Q "((ASSOC == 'exe') || (ASSOC == 'pid')) and (USER == 'yamato')"
    COMMAND        PID   USER ASSOC MODE TYPE SOURCE MNTID      INODE NAME
    lsfd        690292 yamato   exe  ---  REG   dm-2     0   34474245 /home/yamato/var/util-linux/util-linux/.libs/lsfd
    lsfd        690292 yamato   pid  ---  REG   nsfs     0 4026531836 pid:[4026531836]
    pidns      1458677 yamato   exe  ---  REG   dm-2     0   34212178 /home/yamato/var/kernel-essential-training/container/pidns
    pidns      1458677 yamato   pid  ---  REG   nsfs     0 4026533715 pid:[4026533715]
    fd-catalog 1677961 yamato   exe  ---  REG   dm-2     0  128715536 /home/yamato/var/fd-catalog/fd-catalog (deleted)
    fd-catalog 1677961 yamato   pid  ---  REG   nsfs     0 4026531836 pid:[4026531836]

Signed-off-by: Masatake YAMATO <yamato@redhat.com>