Remove 'metadata' and 'category' parsing from pkgmgr_process_* functions
- pkgmgr_process_* functions will no longer call any plugin,
- pkgmgr_parse_* functions will follow old behaviour,
- export __metadata_t and __category_t structures for app-installer plugin loading,
- export enumaration for metadata plugin call.
Following changes should be submitted together:
- https://review.tizen.org/gerrit/#/c/59029/
- https://review.tizen.org/gerrit/#/c/59028/
- https://review.tizen.org/gerrit/#/c/59030/
- https://review.tizen.org/gerrit/#/c/59031/
Change-Id: Ifdb2acd914077ce8e3fb21b6117d1c192f5834e5