Handle legacy file attachments that lack a file_hash

SMF forums originating from past versions can have a large number of
legacy attachments that lack a file_hash. Currently, the importer
encodes these legacy files with a new file_hash, copies the attachment
over into ElkArte, but then orphans them by not saving the new file_hash
in the ElkArte database.

This update simply identifies the legacy files that lack a file_hash,
then imports them over into ElkArte using a static 'legacy' file hash.
This is a bit of a kludge, but it seems better than the current system
that orphans the legacy attachments.

Signed-off-by: Noteworthy Software, Inc <online@noteworthysoftware.com>
smf import function moveAttachment needs to modify $row['file_hash']

I knew there was a better way. This is the better solution. It enables the generated file_hash to forward in the XmlProcessor doSql function.

Signed-off-by: Noteworthy Software, Inc <online@noteworthysoftware.com>
Merge pull request #39 from nwsw/fix

Handle legacy file attachments that lack a file_hash