Tidy up the project structure a bit

- Move the source files into the src/ directory
- Rename the plugin pro and cpp files to qmldesktop
- Add the build directory to the .gitignore
Update the plugin version number to 0.1

Semantic version numbers start with 0.1 and continue up until 1.0 for
the first stable release.
Fix a bug I introduced in the qmldir file
Update the README
Rename LICENSE to COPYING to match the other Quantum projects
Merge pull request #1 from quantum-os/project_cleanup

Project cleanup