Windows build scripts

### Changelog 
* Add `configure.ps1`, `run.ps1` and `test.ps1`.
* Add `setup.py` that configures py2exe and a bootstraper script that bootstraps OpenBazaar.
* Make `openbazaar` single-process in a frozen environment (like in an exe build where running python.exe is not possible)

### Usage
* In order to configure OpenBazaar from its sources in Windows, one must have Visual Studio 2008 installed first.
* After checking out the source, running `configure.ps1` will install python, GnuPGP and OpenSSL in the `bin` directory and install all required packages via `pip`.
* NOTE: All Windows systems come with the option to run PowerShell scripts disabled. To enable running PowerShell scripts the user must run `Set-ExecutionPolicy RemoteSigned` first in the PowerShell prompt.
* `run.ps1` runs OpenBazaar.
* In order to generate an exe distribution, the command `configure.ps1 exe` calls py2exe. The result files are written in `\installers\windows\dist_exe` directory.