Add Run Above and syntax highlighting for commonly used third-party packages

[flcong]

Thank you very much for the plugin. I am a heavy user of Stata and am not a big fan of the do-editor in Stata. This plugin is very helpful and I add some features that suit my needs and probably other users as well.

The following features are added:

A new command to "Run Above" with argument selection="run_above" and default shortcut ctrl+alt+a. Include widely used third-party Stata commands for syntax highlighting (more could be added depending on needs). This is the first time that I have pulled a request, so please let me know if there is any questions or some procedure that I did wrong. Thank you.

[mattiasnordin]

Thanks for additions! Mattias