improved file size calculation and speeds

This reverts commit 3b33712d.

indexing the full path exeeds the maximum index length for MySQL

initial version of a local storage implementation which will use unique slugified filename on the local filesystem.
This implementation will only be enabled on windows based system to solve the issues around UTF-8 file names with php on windows.

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