cmake: Generate shell and cmd configuration

Generate shell and batch file configuration as for bioformats.  The purpose of these is to allow the user or script or build job running cmake to have a simple means to introspect the version metadata without having to do any messing around with git or the cmake internals.

Depends on https://github.com/openmicroscopy/bioformats/pull/1307

--------

Testing: already tested by the CI jobs, but to test by hand:

- Run cmake
- Check for a file named `config` in the build directory which should look something like this ( http://ci.openmicroscopy.org/view/Failing/job/OMERO-5.1-merge-win/ws/src/components/tools/OmeroCpp/cppbuild/config/*view*/ ):

```
OME_VERSION="5.1.0-m0.4-224-gae8448e"
OME_VERSION_MAJOR="5"
OME_VERSION_MINOR="1"
OME_VERSION_PATCH="0"
OME_VERSION_EXTRA="-m0.4-224-gae8448e"
```

If configuring on Windows, you will also get a corresponding `config.bat` ( http://ci.openmicroscopy.org/view/Failing/job/OMERO-5.1-merge-win/ws/src/components/tools/OmeroCpp/cppbuild/config.bat/*view*/ ):

```
set "OME_VERSION=5.1.0-m0.4-224-gae8448e"
set "OME_VERSION_MAJOR=5"
set "OME_VERSION_MINOR=1"
set "OME_VERSION_PATCH=0"
set "OME_VERSION_EXTRA=-m0.4-224-gae8448e"
```

Both of these can be sourced by their respective shells:

```
. config
```

or

```
call config.bat
```

which will set the corresponding `OME_VERSION*` variables.