Re-implemented switch from BAPIv2 to BAPIv3.

In addition to previous changes made being re-applied:
* A crash due to missing userlists has been fixed.
* Exceptions caused by BAPI have been fixed.

The BAPI DLLs used were build from revision
3223531d71de4740b3a69ec1333d688149f12f85 of the BAPI repository.
Re-implemented BOSSv3 support.
Updated readme with MSVC 2013 requirement and misc changes.
Updated .gitignore for .pyc and .tmp files.
Documented a few features in the advanced readme.
Documented more features.
Finished documenting undocumented features.
More docs tweaks.
Removed "beta" from version strings.
Installer now gets built using NSIS Unicode

It's basically just NSIS, but with better translation support. I don't
have the original NSIS installed, hence the change.
Installer script changes.

* Requirements page removed.
* Prerequisites section added as a required option, installs MSVC 2008 &
2013, Python, wxPython, Comtypes and PyWin32 if required for the
selected install options, and if not already installed.
* Removed unused variables and function.
Fixed MSVC 2013 redist not being installed if missing.
Updated version history for 304.4.
Fixed MSVC 2008 URL and download directories.

Also made installer hide for MSVC redist install, like for Python
components.