Sublime Text: Working integration with fsautocomplete

Main changes:

- add general library of code for sublime plugins
- add specific libraries for this project
- basic integration with fsautocomplete

**This code works only on Windows.**

The plugin and fsautocomplete communicate asynchronously (using threads).

At the moment, it's possible to browse top-level declarations in a .fs file.

Also, the plugin keeps the context in sync with the current file (albeit in an inefficient manner). For example, it's able to look for the corresponding .fsproj file (first .fsproj found in the directory hierarchy above the current file or at its same level) and parse the file on_activated (it parses the file whether it's needed or not).

**How to install**

1. Add `fsautocomplete.exe` et al. to *./FSharp/fsac/fsac*
1. Copy the contents of FSharp to *{Sublime Text Data Path}/Packages/FSharp*
1. Start Sublime Text
1. Open a file that is part of a valid .fsproject structure

(Debug logging is enabled, so the log is pretty verbose.)

You now should be able to browse top-level declarations by pressing <kbd>Ctrl</kbd>+<kbd>.</kbd>, <kbd>Ctrl</kbd>+<kbd>.</kbd> and selecting **Show Declarations**.