Re-Add ZM_PATH_DATA

@connortechnology
I'm not sure if you've noticed my previous attempts to point this out, so I'm creating a pull request.

Since merging pull request https://github.com/ZoneMinder/ZoneMinder/pull/200 zmupdate no longer uses ZM_PATH_BUILD as the default folder for sql files.  Instead, it uses ZM_PATH_DATA.  Please refer to the description in pull request #200 for details.