Feature/shortcuts

[ubidefeo]

This PR implements keyboard shortcuts.
Attention has been made to disable them based on context and wether or not the user is performing operations int he REPL.

The shortcuts are also reflected in the tooltips dynamically replacing Cmd+ with Ctrl+ wether the user is on Mac OS or Windows/Linux

These shortcuts are thought to have direct single Meta Key action for the most immediate ones

Run -> Meta+r
Stop -> Meta+h (h as in halt)
Save -> Meta+s

Holding Alt (Option) will also enable

Run selected -> Meta+Alt+r (also works holding Alt when clicking the Run button)
Will only run the code highlighted by the user.
If they accidentally only select whitespace (double-click on an empty line will do) it will run the whole script.

These other shortcuts require the use of Shift and are not of immediate need

Connect -> Meta+Shift+C
Disconnect -> Meta+Shift+D
Reset -> Meta+Shift+R

Clear Terminal -> Meta+k

Because of Reset, the default Electron shortcut for "Application Reload" is disabled, but the menu item still present and actionable under View > Reload

The default Electron shortcut for "Toggle Developer Tools" is disabled, but the menu item still present and actionable under View > Toggle Developer Tools

Connect and Disconnect work also in the File Manager view, while other shortcuts are disabled.

[sebromero]

Please see comments. I'd use all upper case for the shortcuts and maybe we should figure out how to do this without using global shortcuts.

[sebromero]

Let's get rid of the code in index.js that is commented out and we're good to go.