Use position/direction sampling from base source for radionuclide sources

[ftessier]

This pull request replaces #672. The original pull request branch was removed from the forked repository, so the branch and pull request is hereby reinstated. The original pull request message was:

The implementation of egs_radionuclude_source is changed so that it takes an input "base source" instead of defining a collimated or isotropic source. This way you can use any of the egs sources or a custom egs source to define the location of the radionuclide in the simulation. The change in particular was made towards fast simulations targeted radionuclide therapy across a whole patient phantom.

[ftessier]

Rebased on develop.

[ftessier]

Something ain't right. The second (last) commit reverts apparently legitimate changes, for example adding the name of the contributor and updating the documentation. @MartinMartinov or @rtownson, any chance you can shed light on this? For the record, this pull request was reinstated from #672, from a branch obtained as follows:

git fetch origin pull/672/head:feature-radionuclidesource-sourceimport
git rebase develop
git push origin

[rtownson]

Yes the missing contributor/documentation looks like a mistake, not sure how it happened.

When you re-instate it, change the indentations to use spaces instead of tabs.

[ftessier]

Yes I will run astyle. So are you confirming that the other changes in that commit are all good then? I will attempt to clean it up and wait for review.

[rtownson]

Yes I will run astyle. So are you confirming that the other changes in that commit are all good then? I will attempt to clean it up and wait for review.

Yes, the comments from the first commit are correct. The code added in the second commit is also correct.

This PR breaks backwards compatibility - users with radionuclide sources will have to update their input files. I think that's OK, maintaining backwards compatibility would result in a lot of duplicate code.

[ftessier]

@rtownson I think I got it sorted out with the last push. Can you take a look? Applied astyle.

[rtownson]

@rtownson I think I got it sorted out with the last push. Can you take a look? Applied astyle.

Yep, looks right!

[rtownson]

I'm going to add one more commit to add a check for the old deprecated inputs, and give a description of the new format.

[ftessier]

Rebased on develop, squashed and tweaked commit message. Also, remove the year from the contributor line in the header, to match EGSnrc style (only the author has the year indicated, to preserve pre-git history; now contribution date is provided by the git log)