#319 Add Smart Extract context menu option

[Michael]

Provides closure for feature requets 1272, 1206, 1147, half of 1139, and likely more. Basic function of this is to "Extract here" if the zip contains one file, otherwise "Extract to ".
This is untested, and likely incomplete. I'm not well versed in C++, and have not been able to compile 7zip (makefile issues and lack of documentation for finding/installing VC++6.0 so I likely messed that up), but I have done as much as I can, to my knowledge, to ensure there are no syntax errors or anything to fail compilation.