Added DSA signature verifier.

DSAVerify takes in a file that is signed and checks with its signature and
public key to find if it is valid. Tests also written for this.
Added a DSA generator and signer.

These classes generate DSA keys and sign files with them. Both DSAGenerate.java
and DSASign.java can be run from the command line.
Made DSASign.java save the signature to a file.
Put DSA sign programs in a tools/ dir.

This is so that people using this program can easily use these
tools to generate DSA keys and sign files with the DSA keys.
Merge branch 'feature/SignatureVerify'

Completed DSA signing features.