Drop ALL C++ code from this code.

This package (in practical terms, which means the features we use the most) has three base functionalities.

1. With the support of bob.io.image it reads and writes images (bob.io.base.load and bob.io.base.save)
2. Reads and writes HDF5 files with matrices with the command bob.io.base.load and bob.io.base.save.
3. Support to read and write complex HD5 files

I'll rewire the bob.io.base API to

1. use imageio for reading and writing image formats (solving 1);
2. use h5py for reading and writing hdf5 files (solving 2);
3. rewrite pieces of code that use the complex HD5 files using h5py (solving issue 3).

Sounds reasonable enough?

ping @amohammadi @ydayer @flavio.tarsetti @mguenther @lcolbois