* [eigen3] Fix generated pkgconfig files

* [ignition-cmake2] Update to C++ library

Now ignition-cmake also installs a C++ library, so
it is possible to remove code specific for CMake-only ports.

* [ignition-modularscripts] Fix pkgconfig files installed by ignition libraries

Use the new function vcpkg_fixup_pkgconfig to fix the installed .pc pkgconfig files
of the ignition libraries.

As ignition-fuel-tools1 depends on curl that has a broken pkg-config file, disable
installation of its pkg-config files.

As announced in https://community.gazebosim.org/t/important-gazebo-and-ignition-are-going-to-github/533,
the ignition project repositories have been migrated from BitBucket to GitHub.

This commit updates the ignition_modular_library helpers to use GitHub instead of BitBucket,
and also update the hashes of all the ignition ports as apparently the archive generated by GitHub
for releases are slightly different from the one generated by BitBucket.

* ignition-modularscripts: move CMake config files only if necessary

Some ignition libraries (such as ignition-cmake2) already install the
CMake config file in the location required by vcpkg

* Add new port ignition-cmake2

Add new port for the ignition-fuel-tools version 1, part
of the Ignition Robotics Libraries (https://ignitionrobotics.org/).

* Add ignition-modularscript port

Modeled after the qt5-modularscript port, this port just contain
ignition_modular_library, an helper CMake function to simplify the
process of writing port of C++ libraries developed by the Ignition
Robotics project ( https://ignitionrobotics.org ).

* Add ignition-cmake0 port

* Add ignition-math4 port