Evaluate accuracy with hybrid SEP(2) for different approximation
orders for the perturbation.

Compute share of the gap between SEP and exact solution closed by increaseing the approximation order.

- Introduce fourth-order perturbations
- Remove SEP(10) with the complete tree
- Cosmetic adjustments

Also display results as soon as possible.

Use latexindent Perl script.

Also:

 - Fix font size in Tikz plots
 - Add colors (provisions for IRFs with stochastic perfect foresight models)
 - Change notations for the paths of endogenous variables

With and without irreversible investment.

With SEP order=0:10.

Without labour supply and with a CD instead of a CES production
function. Also the lower bound for investment is not zero but a
positive fraction of the steady state.