cv::KeyPoint may not be saving/loading as intended

[ymd-stella]

Describe the bug

When saving maps to sqlite3, cv::KeyPoint may not be saving/loading as intended. The following warning has been issued.

/openvslam/src/openvslam/data/map_database.cc:538:76: warning: 'void* memcpy(void*, const void*, size_t)' writing to an object of type 'class cv::KeyPoint' with no trivial copy-assignment; use copy-assignment or copy-initialization instead [-Wclass-memaccess]

Environment

• CPU: Intel
• OS: Ubuntu18.04
• Commit id: 64f4f63
• Install procedure: docker

Additional context

Related to #269.

[ymd-stella]

@BBin1103 Thanks for the report, but please create another issue because it is irrelevant to this issue.

[BBin1103]

@BBin1103 Thanks for the report, but please create another issue because it is irrelevant to this issue.

ok, #308