Numerical Integration for common outer moments

[JGLee6]

We do not currently know of any closed form expression for the outer moments of simple shapes centered about the origin to arbitrary order. A method to numerically integrate for the lowest order moments of several common shapes may allow for more precise calculations than available through PointGravity calculations of outer moments.

• [x] a method to list the moments at arbitrary order for various (l, m) in cartesian or cylindrical coordinates
• [x] Or an explicit list of moments for the lowest orders
• [x] Use of scipy.integrate (maybe tplquad)
• [x] various hard-coded bounds of integration for several shapes

The same techniques could be applied to Yukawa moments or to shapes without analytical closed-form solutions.

[JGLee6]

Some of this code has been added to the branch newtv2 on my fork, but has not been tested at all. It makes use of a cylindrical expansion for the irregular solid harmonics at any (l, m) allowing us to calculate out to any order we might want to burn CPU time on. It uses scipy.integrate.tplquad. Needs:

• [x] test annulus moments vs explicit outer moment to L<=5 in bigQlm.py
• [x] test cone and trapezoid vs PointGravity
• [ ] maybe make rectangular solid as well