Patch - Wait before exiting iterator due to minor eigenvalue change

Small patch to iterator/itermain function. If the initial eigenvalue is close to the target, then the change between the first and second parameter may be small. This causes the second eigenvalue to be very similar to the first, and raised an exit. The linear iteration variable update moves on past this, and the third iteration variable will experience more of a change, thus causing a more noticeable change in eigenvalue for well defined problems.

This bug has been squashed by simply increasing the required iteration wait times by one.

v2.0.0

Improved iteration procedure

After an initial scaling, the iteration variable is updated using a linear extrapolation off the previous two values and their subsequent errors from the target eigenvalue.

Improved modular structure

Gone is the terrible globalparams file, here is the new, more modular and importable structure.
Each main module (iterator, readinputs, outputs) can now exist on their own and be imported into other python projects.

Documentation

A very rudimentary pdf has been added in docs/pdf that contains documentation on the functions.
This will be expanded and improved in future releases.