vim: implement gvim, vim-tiny as PACKAGECONFIG

* only one of those should be built in sysroot, otherwise they were
  overwritting files provided by other alternatives
* define PACKAGECONFIG options
* there are no RCONFLICTS/RREPLACES/RPROVIDES, because it depends on
  selected PACKAGECONFIGs
* add PN to VIMDIR and use VIMDIR where undefined VIMVER was
  (e.g. "${PN}${VIMVER}")
* move checksums from .inc to recipe
* vim/gvim/vim-tiny conflict is now fatal, with
  http://patches.openembedded.org/patch/43105/



Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>