[new-stino] Update menu_main.txt

Fix some path problems with settings and keybindings files in `Preferences > Package Settings > Stino (Arduino Like IDE)` menu.

Please note that because of the hardcoded package path, we know need to use a definite name, so I've used `Stino` which is cleaner than `Stino-new-stino`.
A proper removing of the older version is needed before installating this new version:
  * Click the menu `Preferences->Package Control->Remove Package->Stino-new-stino`
  * Restart Sublime Text
  * Install new version in `Packages/Stino` folder

I have edited the installation instructions in issue #179 accordingly, sorry for any inconvenience.