Move dependencies in 'external' directory and pdate git submodules

external/Catch2/.github/pull_request_template.md

@@ -0,0 +1,28 @@
+<!--
+Please do not submit pull requests changing the `version.hpp`
+or the single-include `catch.hpp` file, these are changed
+only when a new release is made.
+
+Before submitting a PR you should probably read the contributor documentation
+at docs/contributing.md. It will tell you how to properly test your changes.
+-->
+
+
+## Description
+<!--
+Describe the what and the why of your pull request. Remember that these two
+are usually a bit different. As an example, if you have made various changes
+to decrease the number of new strings allocated, that's what. The why probably
+was that you have a large set of tests and found that this speeds them up.
+-->
+
+## GitHub Issues
+<!-- 
+If this PR was motivated by some existing issues, reference them here.
+
+If it is a simple bug-fix, please also add a line like 'Closes #123'
+to your commit message, so that it is automatically closed.
+If it is not, don't, as it might take several iterations for a feature
+to be done properly. If in doubt, leave it open and reference it in the
+PR itself, so that maintainers can decide.
+-->