Move from deprecated QtScript to QJSEngine
Remove unused source files.
Merge pull request #97 from Hello71/qjsengine

Move from deprecated QtScript to QJSEngine
Merge pull request #98 from Hello71/unused

Remove unused source files.
Remove OS-specific entries from .gitignore.

.gitignore should only store items that are generated by the code in the
repository. If your operating systems generates temporary files, put
those in your .gitignore_global.