Refactored safeword_list_tags().
Fixed segfault when listing all tags; quick fix was to duplicate code.
Added safeword_list_tags() unit tests.
Fixed a couple bugs in safeword_list_tags() when filtering. Implemented unit test for filtering.
Changed safeword_tag_info() to safeword_tag_read(); updated its implementation.
Refactored list tests to use its own suite init to avoid static data name clashing.
Fixed logic issue in safeword_credential_read() that never read tags.
Implemented skipping reading tags if there are none.
Initial tag unit tests.