Ensure small/large angle approximation flag used for error maps

[lukeje]

The check for the small angle approximation flag was within another if statement which checked for the presence of a flip angle map, and so could unintentionally be skipped. This is fixed by the current pull request. I also took the liberty of correcting some typos, formatting issues and inconsistencies in the documentation for these functions.

This bug will have given rise to incorrect error maps in the case where the toolbox was run with small_angle_approximation=false and with either the UNICORT option or no supplied transmit B1 field map. In this case the error maps would be incorrect and so map creation should be rerun after applying this fix.

[lukeje]

@Barisevrenugur I assigned this to you to get a second pair of eyes on it before pulling. I hope it's pretty simple; let me know if you don't have time so I can ask someone else.

[Barisevrenugur]

@lukeje I am working to finish up other things but yes I can give a look to this one, the code change is not very extensive. but in a nutshell the code change is the following right? : if there is no B1 correction (f_T is empty) the small angle approximation is still applied, in the case when f_T is not empty (there is B1 correction), current change gives the same execution flow with the previous code

@Barisevrenugur I assigned this to you to get a second pair of eyes on it before pulling. I hope it's pretty simple; let me know if you don't have time so I can ask someone else.

[lukeje]

@siawoosh I've added you as a reviewer so that you are made aware of this bug. I can't even remember why we might have implemented it with the small angle check inside the B1 map check...