Improvments to default directories

[Nick Draper]

Add a userSearch.Directories key this is for mask files grouping files etc, and would clear the datasearch purely for data files.

You would need to add anther argument to the file property, and enum to select which directory list to use (data, user, None).

You should be able to override these values in the configService in C++ (changes them for this session).

The python interface should allow users to alter these through a settings function on the FrameworkManager.

Perhaps add a save functionality to the ConfigService to save altered values to the user.properties file.

[Roman Tolchenov]

(In [4726]) Added Directories tab to the Mantid page of the Preference dialog box in Mantidplot. re #1024

[Roman Tolchenov]

(In [4797]) Added python and instrument directories to MantidPlot preferences dialog box. re #1024

[Steve Williams]

(In [4815]) In the Mantid default settings tab I've removed the repeated titles re #1024

[Nick Draper]

Moved to verify state

[Martyn Gigg]

The MantidPlot preferences look okay.

However, I can find no reference to the userSearch.directories key. Is this ticket actually complete?