Cygwin setup 2.830 properly handles dependencies now (version 2)

Changelog:

- Removed package dependencies, as Cygwin setup 2.830 no longer requires them to be listed.
- Changed mirror to http://mirrors.kernel.org/sourceware/cygwin/ for speed.
- Replaced hardcoded C: drive references with %SYSTEMDRIVE%.
- Hardcoded architecture to "x86" as "x86_64" seems a bit buggy still.
- Changed temporary directory from C:\WINDOWS\temp to %TEMP%.
- Added additional comments

I tested these changes, and the boxes

````
win2008r2-datacenter
win2008r2-enterprise
win2008r2-standard
win2008r2-web
win7x64-enterprise
win7x64-pro
win7x86-enterprise
win7x86-pro
win81x64-enterprise
win81x64-pro
win8x64-enterprise
win8x86-enterprise
````

successfully install OpenSSH, and VMWare Tools.

The boxes

````
win2012-datacenter
win2012-standard
win2012r2-datacenter
win2012r2-standard
````

*sometimes* fail to build, as the sshd service logs the following error when it's started:

`sshd pid service sshd failed signal 11 raised`