by smk-ka: Fixed a bug in demo_reset() where long lines could be partially crippled, resulting in broken imports. This happened when a chunk of data in the middle of long line started with a comment sign, causing the import function to discard it.

- Export excluded tables' structure (using IF NOT EXISTS) to facilitate the creation of a new site from an existing demo dump.

- #175498 by smk-ka: Added version number to dumps to distinguish new-style from legacy dumps that included the watchdog table.

Added sort snapshots by date.
Added changelog.

- Switched to extended insert format, which is much faster on importing than separate insert commands.

- Excluding watchdog table from dump/restore. Watchdog will stay intact even after restore.