code clean
show error message if error caused while sending password
fix sql injection in send_pass
renamed:    upgrade-finished.html -> upgrade-finished.html.php
db converted to InnoDB; improved db upgrade script; script db version bumped to 19
update mysqli db creatoin cshema to v19 (innoDb + bytes in attachment)
remove mysql creation schema. it's duplicate mysqli schema
+ PdoAdapter->getPdo()
new attachment system. attachments stored in db
bump version to 1.5.3
stop working if db version very low
fix messages in upgrade.php
+ inc/UpdateChecker.php
check for updates and show message if update found
bump db version to 20 in install progress
strict mode for all by default
update README
update CHANGELOG
update UPGRADING
update INSTALL