Automatic generation of Doxygen documentation

[guitorri]

Just to let you know that Travis is setup to automatically build and publish the Doxygen documentation.

See:

• https://github.com/Qucs/qucs-doxygen

For the moment the Travis script is in the ci-build-deploy-doxygen. Soon I will merge and set it to build only merges to the master branch.

I hope it will encourage everyone to update/improve the code documentation strings.

Comments are welcome.

[guitorri]

Automatic generation of Doxygen source code documentation is now operational. Only the master branch is being built and deployed.