\brief Coefficients for the projections of the elemental basis functions
from coarser to finer elements and vice versa.

The MODG scheme is defined with Legendre polynomials (ansatz functions)
and modified Legendre polynomials (test functions). Because of our
dimension-by-dimension approach we can consider 1D elements without loss
of generalty. \n
For MODG scheme the reference element is always \f$ [-1,+1] \f$ . In case
of non-conforming element refinement we have the follwing faces overlying
in the 3D case: \n
\n
faces of refined face of non-refined
cube cube
------------------------ ------------------------
| | | | |
| 3 | 4 | | |
| | | | |
------------------------ <----------> | 5 |
| | | | |
| 1 | 2 | | |
| | | | |
------------------------ ------------------------
\n
To enable flux calculations and projections between the two element sizes
we have to tansfer polynomial functions from one element size to another
one. \n
Therefore we have two tasks: \n
1. Restrict polynomial functions on 5 to each of the fine element 1 to 4.
The restriction has to deliver a polynomial approximation on 1 to 4
in terms of fine element's ansatz functions. \n
2. Approximate polynomial functions on 1 to 4 by a L2-projection on 5.
Again the approximation on 5 has to be delivered in terms of ansatz
functions defined on 5. \n
Without loss of generaltiy we can restrict ourself to the following 1D
situation: \n
\n
\n
Coarse face's ref. element \n
f(x) \n
| ------- \n
| / \ / \n
|/ \ / \n
| \ / \n
| ----- \n
|----------------------|-------------> \n
-1 +1 x \n
\n
/|\ | \n
| | \n
L2 proj. | | L2 proj. \n
(approx) | | (exact) \n
| |/ \n
\n
Fine face's ref. element \n
f(x) f(x) \n
| ------- | \n
| / |\ / \n
|/ | \ / \n
| | \ / \n
| | ----- \n
|----------|--> |-----------|--> \n
-1 0 x 0 +1 x \n
\n
This datatype stores all the coefficients to calculate the necessary
L2 projections to transfer polynomial functions between coarser and
finer elements (, faces and volumes).

1st dim: standard anzatz function [-1,1]
2nd dim: shifted anzatz function
3rd dim: shifting for coarse basis function
1: 1/2x|y|z - 1/2
2: 1/2x|y|z + 1/2

Nodes of different colours represent the following:

Solid arrows point from a derived type to the parent type which it
extends. Dashed arrows point from a derived type to the other
types it contains as a components, with a label listing the name(s) of
said component(s).