phenix.map_value_at_point: tool to compute map value at a given point using eight-point interpolation.

- Inputs:
- MTZ file containing Fourier map coefficients;
- label selecting which map coefficients should be used (in case there are multiple choices in input file, there is no need to provide label otherwise);
- the coordinates of points at which the map value will be computed can be defined in two ways: either providing a triplet of xyz coordinates using 'point' keyword, or giving a PDB file in the command line in which case the atomic coordinates will serve as points;
- optionally the 'resolution_factor' can be specified. It defines the map calculation grid step as grid_step=resolution_factor*d_min
- optionally, type of map scaling can be defined: sigma or volume scaled (sigma is the default).

- Usage examples:
- phenix.map_value_at_point map_coeffs.mtz point="0.5 1.2 3" point="0.53 3.3 2.5" label="2mFo-DFc"
- phenix.map_value_at_point map_coeffs.mtz model.pdb
- phenix.map_value_at_point map_coeffs.mtz model.pdb point="1 2 3" resolution_factor=0.3

IMPORTANT: point must be a triplet of Cartesian coordinates (not fractional)!

- Output:
- list of map values at specified points.