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.
Use process_vm_{read,write}v instead of ptrace

This approximately doubles the speed of Dwarf Therapist on Linux, and
fixes #73.
Silence bad address errors.