Split geowiki paths in base path and scripts

This preparation step allows to move the checkout of the geowiki
scripts around more easily in follow-up commits.

Change-Id: I80ea50c0fcc9e53f1f1a92a1ef0a7aa7f08179f3
Move geowiki scripts into geowiki's scripts subdirectory

Since we'll be adding a repo for geowiki's private data, and a bare
repo for it, following the current layout, we'd arrive at:
  /a/geowiki
  /a/geowiki-data-public
  /a/geowiki-data-private
  /a/geowiki-data-private.bare
. Four geowiki directories in /a seems too much. So we move
/a/geowiki -> /a/geowiki/scripts, and can work towards having all of
them underneath /a/geowiki:
  /a/geowiki/scripts
  /a/geowiki/data-public
  /a/geowiki/data-private
  /a/geowiki/data-private.bare

Change-Id: Ib7bada6e099a2f05a7b459cc96fbc6d21f43f23c