Fill in readme with overview from wiki page, plus link to it
relocation of files

[root]
 + src/  ... source code of host & device
 + test/ ... regression tests
bugfix: gpupreagg created KDS_ROW for row-by-row mode, but it should be KDS_ROW_FLAT!
bugfix: referenced device type didn't update extra_flags

It leads lack of #include "opencl_*.h", then made undefined data
type error.
Merge branch 'master' of https://github.com/aeischeid/devel into aeischeid-master
add basid README stuff
Merge branch 'aeischeid-master'