* Add upgradecores function to prepare script.
Differences from preparebinonly:
- If with/withoutcoins isn't set
- Read list of coins to update from basicswap.json
- Only where manage_daemon or manage_wallet_daemon is true
- Store core version no in basicswap.json
- Only update if missing or differs.
- Writes core_version_no and core_version_group to basicswap.json
- Per core updated
- Backup old config to timestamped file
* Upgrade unmanaged coin cores by default.
Disable with BSX_UPDATE_UNMANAGED.