bitcoind without wxWidgets

I replaced the last of the few wxBase dependencies in bitcoind.

bitcoind now compiles without wxWidgets or wxBase in SVN rev 112.

main(int argc, char* argv[]) is added to init.cpp.  CMyApp and the Startup folder stuff are moved to ui.cpp.  ui.cpp and uibase.cpp aren't linked by bitcoind.

The makefiles have -DGUI to control whether the GUI is used.

I test compiled MinGW, VC and Ubuntu.  I don't know if I broke the Mac OSX build, someone will need to check that.