Improve error messages and user-friendliness in general about steganography HOT 4 CLOSED

In LSBSteg, we now detect when a user requests to hide more data in an image than is possible (0f675ff).

We also now check for the required command line arguments in LSBSteg (55afb45).

• Analysis requires an input image and input secret.
• Hiding requires an input image, input secret, and output image.
• Recovery requires an input image and output file.

from steganography.

We now check for the required command line arguments in StegDetect and WavSteg (16b7758).

• StegDetect requires an input image.
• WavSteg hiding requires an input sound, input secret, and output sound.
• WavSteg recovery requires an input sound, output file, and number of bytes to recover.

from steganography.

We now allow LSBSteg analysis without an input secret/payload (4839c15).

from steganography.

We now also check for impossibly large filesize tags in LSBSteg recovery (see #4 and 4b582bc).

from steganography.