changed core config namespace to "core"
rex_user: renamed column "user_id" to "id"
rex_template: removed unused column "label"
rex_module: removed unused column "category_id"
rex_metainfo_params: renamed column "field_id" to "id"
rex_media: renamed "media_id" to "id", removed "re_media_id"
rex_config: renamed "cid" to "id"
rex_article: renamed "startpage" to "startarticle"
rex_article: removed unused column "attributes"
rex_article_slice: removed obsolete columns "html" and "php"