Some minor cleaning up [ci skip].
Some work on the list for CellML warnings/errors (#360) [ci skip].
Some minor cleaning up [ci skip].
Some minor cleaning up [ci skip].
Some work on the list for CellML warnings/errors (#360) [ci skip].
Some work on the list for CellML warnings/errors (#360) [ci skip].
Remove Qt deprecated code (closes #397).
Some work on the list for CellML warnings/errors (#360) [ci skip].
Some work on the list for CellML warnings/errors (#360) [ci skip].
Some work on the list for CellML warnings/errors (#360) [ci skip].
All the use of [Enter] to open a file in the file browser/organiser
window plugins (closes #398).
Some minor cleaning up [ci skip].
Some work on the list for CellML warnings/errors (#360) [ci skip].
Travis-CI: use homebrew to install CMake on OS X.

Indeed, for some strange reasons, to get the CMake binaries for OS X
doesn’t seem to work anymore (see
https://travis-ci.org/opencor/opencor/builds/30246404).
Travis-CI: use homebrew to install CMake on OS X.
Some minor cleaning up [ci skip].
Some minor cleaning up [ci skip].
Some work on moving some widgets to their own plugin from the Core plugin (#396) [ci skip].
Revert "Some work on moving some widgets to their own plugin from the Core plugin (#396) [ci skip]."

This reverts commit 0ad33124db1962fbbc119b28cf3ddd88dc5d7549.
Some work on having Oxygen icons used by a given plugin in the plugin itself (#399) [ci skip].