Remove possibility to set own folder path in each folder

Phenomenon

A common failure when using YAM seems to be that users misconfigure their path settings of new custom folders so that they end up in an incorrect path setup which might delete important files, thus data.

Background analysis

The problem seems to be that users currently have the complete freedom of moving different folders to completely different root pathes by entering a complete directory path including the disk identifier. The solution for this common problem is to limit users in only entering a directory name for a folder which is always relative to the mail directory configured in the user configuration file (PROGDIR:.users)

Implementation recommendation

Care have to be taking in how the user configures the directory name in the folder configuration as it should be prevented that he enters characters which are not allowed in directory names (e.g. ':', '/', etc.). Furthermore it should be investigated if the directory could be automatically generated via the folder name if possible.