cape.dkit.dbll: Aerodynamic line load DataKits

This module provides customizations of cape.dkit.rdb that are especially useful for launch vehicle line load databases. The force & moment coefficient names follow common missile naming conventions:

Name	Symbol	Description
CA	$C_A$	Axial force
CY	$C_Y$	Side force
CN	$C_N$	Normal force
CLL	$C_{\ell }$	Rolling moment
CLM	$C_m$	Pitching moment
CLN	$C_n$	Yawing moment

Line loads are typically defined for the force coefficients, and the standard for these is to have dCN as a column name, which actually represents the value

\[\frac{\Delta C_N}{\Delta x/L_\mathit{ref}\]

In the limit of finer slices, this becomes $\mathrm{d}{C}_N/\mathrm{d}x/L_{\mathit{ref}}$. In other words, the primary data is the derivative of a force coefficient with respect to the non-dimensional x-coordinate.