Windows Support and GSM Module Functionality

###Summary
I updated pymomo.commander to include proxy objects for sending text messages and AT commands.  I also tweaked the build system to run correctly on Windows.  Issues were that spaces in filenames were not properly escaped and Windows loves having spaces in file names.  Also modtool did not properly detect the field service unit because pyserial returns a different string on Windows 7 than linux.  I added a check for the Windows 7 version.

Finally I added mibtool build to build mib12 application modules.  It just invokes scons internally but gives it the appropriate --site-scons argument so it can find our build tools.  
Usage:
```shell
$ mibtool build <scons arguments>
```

It is invoked exactly like scons and all arguments after build are forwarded on to scons for processing.

###Windows Support
Compilation and building is now supported on Windows.  It has been tested only on Windows 6 64 bit though.  Initially I tried to use cygwin but cygwin is unworkably slow (known issue apparently) on 64 bit Windows 7.  Evidently lots of programs use fork internally and fork is emulated on windows and very slow.  Also, path handling between cygwin and regular windows is a pain b/c they have separation namespaces for file paths.  C:\ is /cygdrive/c under cygwin.  This screws up xc8 which expects windows paths and python compiled under cygwin which provides cygwin paths.  

After trying some things I settled on not requiring cygwin and using either git bash or just the standard Windows Command Line.  This is described on the wiki in the Windows-Installation link from the getting-started page.

###Known Issues
* mibtool build cannot yet do parallel builds.  Invoking with -jN causes it to become nonresponsive and need to be killed.  It's not clear why since the implementation should be almost the same as the scons script itself.