Switching to cmake.

A few notes:

1) I re-organized the directory structure in the process.

2) Archive plugin is not included for now. Major refactoring require for
archive plugins. Plan is to convert archive plugins to input plugins.

3) Eerything that does not have external dependencies are always
enabled. I've gone through the code, those features will not increase
the result executable size too much.

The conversion to cmake is considered done by now. Future changes will
be in separate commits.