[AndyB] Convert image all 5.8

Added code to prevent server error if embedded meta data is empty.

Updated regex to fix issue with multiple IMG tags on same line.

Fixed issue with try / catch code.

• Attachment tables xf_attachment and xf_attachment_data are now updated more accurately to reflect original post date and post user id.

• Fixed issue when multiple IMG tags were on the same line.

Now retains IMG bbcode options.

Now supports alt text in the IMG bb_code. Now excludes posts and threads which are not visible.

• Now support hot linked images using Alt text in IMG tag.

Fixed issue with dead link causing server error log.

Convert image all v4.6 changes:

Removed function which converted Proxy images.