Clean some shit up in the header

- Apparently it's not good practice to use a namespace in a header, so
I took that out.
- AJ made a good point about using a linear vector, so I took out some
of the 2d stuff as it was unnecessary.
Add file import/export member functions

These are fully functional. The exported file exactly matches the
original.
Add command line functionality

Command line accepts filenames in the format:
./bitmap inputFile outputFile -(o/h) (overlayImage if applicable)