* Allow arbitrary listing base directories

Unfortunetally this breaks themes which attempt to check whether a file exists
or is of a certain type if the base directory does not match the current
working directory. Each entry in $dirArray now provides the 'real_path' item
which can be used if the actual file path of an entry is required.
Added new configuration option 'relative_paths' and made it default.
It will generate paths relative to $_SERVER['SCRIPT_FILEPATH'] directory
instead of absolute on the $_SERVER['DOCUMENT_ROOT']. This restores
compatibility to themes using 'file_path' instead of 'real_path' to perform
file operations. Can be considered a fix for bug #25 now.

All previous changes to `index.php` have been reversed. No changes to this
file are required on update now.

Added configuration option 'date_format' which allows the user to set his/her
preferred date formatting.
Merge branch 'master' of https://github.com/DirectoryLister/DirectoryLister

Conflicts:
	resources/DirectoryLister.php
	resources/themes/bootstrap/index.php
Added support for directory index files
Fixed loading of external resources