add parent directory to the file cache if it does not exist yet.

fix for bug #1942: Allow user to share with every group if "allow users to share with anyone" is set

TODO for OC5: use CURRENT_TIMESTAMP for all databases. mysql supports it as a default for DATETIME since 5.6.5 [1]
as a fallback we could use <default>0000-01-01 00:00:00</default> everywhere
[1] http://bugs.mysql.com/bug.php?id=27645
http://dev.mysql.com/doc/refman/5.0/en/timestamp-initialization.html
http://www.postgresql.org/docs/8.1/static/functions-datetime.html
http://www.sqlite.org/lang_createtable.html
http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions037.htm

put all the calls into one function and use tabs instead of spaces. Thanks to danimo for bugging me :-)

add a sane socket timeout so that the interface stays responsive with a slow or not working internet connection

use socket timeout of 10 sec to stay responsive even with a slow internet connection or a not working server

we are sharing the same file again if item_source of the already shared file and the newly shared file is the same. Therefore we can use the same target name

automatically remove and prevent installation of apps with a require version less than the current one. We check now the first ad second part of the version number.
Also increase the require tags of the core apps to 4.9 Please note that 4.9 is the internal versionnumber of the upcoming 4.5 release.
You have to pu a <require>4.9</require> into the info.xml of your app to make it as compatible with 4.5

fix create folder and upload file issue on win, fixes oc-1747, solution follows suggestion from bug tracker