LFI Scanner : Fixed apache log code injection technique + LFI dectection improvement

Fixed apache log code injection technique:
- It did not work as it wasn't properly injecting PHP code in it
- There is still a flaw to fix : it doesn't take into account the max
  length of a log line

LFI detection improvement:
- Added /etc/passwd test
- Added NULL byte injection test
- Need more improvement on error message detection

This code has been tested to work with phpLDAPadmin 1.1.0.5, DVWA and
multillidae.