Suggestions from an user of minor things to change/improve

1. Installation instructions

- Within the [installation instructions for MATLAB](https://github.com/CERN/TIGRE/blob/master/Frontispiece/MATLAB_installation.md) under the Step by Step Instructions > step 6 it suggests modifying line 125 mex .xml file but I found this is only correct for the earliest version MSVS mex file and all other are later on. For example I have MSVS2019 installed and had to modify line 266.

- Windows defender seems to be blocking matlab mex files. Add docs about this.

2. InitTIGRE.m

- line 41 & 77 - pCTMexFiles sub-directory did not exist. I'm not sure when this directory is supposed to be created but had to manually add in an empty path of same name to get InitTIGRE to work (note, I am not intending to use proton CT as part of my work).

3. CompilePCT.m Running CompilePCT returned an error:

- line 1 - a rogue 'C' at start of line

- line 121 - as part of the try loop using 'readlines' (not sure where this function is).

4. Demos>d23_DualEnergy.m

- line 19 - first argument to the VarianDataLoader function should be datafolder_low

5. Utilities>DE>DeDecompose.m

- line 42 - I think this needs changing as it depends upon the level in directory at which the user is calling this function, e.g. for me when running the d23_DualEnergy.m demo it did not work as the dual energy demo file is located one level higher than DeDecompose.m and so the relative file path in the code did not work (.\MATLAB\Demos\d23_DualEnergy.m vs .\MATLAB\Utilities\DE\DeDecompose.m). If useful I have replaced this line with the following:

```
temp = cd;
[start, ~] = regexpi(temp, [filesep 'MATLAB']);
fid = fopen([temp(1:start-1) 'Common' filesep 'data' filesep 'dual_energy_calibrations.json']);
clear temp
```
6. Utilities>DE>MakeVMproj.m
- line 12 - same issue as DeDecompose.m line 42

Start with Frontispiece/MATLAB_installation.md, InitTIGRE.m, and CompilePCT.m to verify the installation and compilation reports. Then inspect Demos/d23_DualEnergy.m, Utilities/DE/DeDecompose.m, and Utilities/DE/MakeVMproj.m, comparing their paths and arguments with the reported failures. Done means the documented setup and affected demo or utility paths work without the reported errors.

Written by the indexing model from the issue text.