Support a list of CSVs for a file table entry path's value

This commit adds support to the FileTable constructor to accept
a list of comma separated values for the value of the "path"
property in the file entry records declared in fileTable.json. The
list's order defines the priority, meaning the first path, if
it exists will be used, then the next is considered, and so on.
This will allow the file table to support files who should consider
patch directories.

Change-Id: Id543946ef93a9f380576def9d68c1c4ab13bf7fc
Signed-off-by: Christian Geddes <crgeddes@us.ibm.com>