remove the index on the share table because of problems with the index size. Thanks to icewind for spotting this.

add a few more indexes. This is just a first step. More work is needed here but this should improve perfomance already for big installations.

set configuvalue in table appconfig back to clob. Likely to break LDAP settings, probably responsible for some bugs with it. Might also cause damage in other apps. That's why it was once already set to clob

fix default values: 1. remove whitespace, don't use emptystring for int, remove empty default for nullable columns to use NULL as default

Changed oc_preferences configvalue back to clob as it will give us bug reports in calendar, contacts and tasks if less.

add length to text columns or newer mysql will produce columns too wide

use CURRENT_TIMESTAMP in default column definitions (sqlite, mysql, postgres and oracle DO understand it), change clob columns to text (clob will give sorting and uniqueness problems and in general is not what we want)