Merge branch 'develop'

* develop:
  README.md: Add link to release notes

[cmake] Rationalise names of tests vs targets

Cherry-picked from develop branch commit 4dc3836
ignoring changes in all `CMakeLists.txt` files but this one
`test/extension/toolbox/CMakeLists.txt` which somehow missed the changes.
Possibly due to my mistake during previous cherry-picks to compose
the emergency fix boostorg#394 for docs in `master` branch, that also
brought the restructuring of the tests directories.

Missing changes in `test/extension/toolbox/CMakeLists.txt` file
are currently causing failures of AzP builds using CMake
for `master` Boost 1.72 merge e8a04f4
This is attempt to fix it in the `master`.

Add build-project color missing from test/Jamfile

Add build-project color missing from test/Jamfile

Add build-project color missing from test/Jamfile

Use class for template template parameter (boostorg#251)

The current definition using `typename` fails when compiling
with GCC 4.8 and 4.9, because `typename` is allowed since C++17.

Clean up several warnings about unreferenced formal parameters

Add comment to premultiply.hpp:
- FIXME: Is c input paramater not used intentionally?

Clean up several warnings about unreferenced formal parameters

Add comment to premultiply.hpp:
- FIXME: Is c input paramater not used intentionally?

Fix (some) warnings.

Removed executable attribute from files.