Convert image 5.1

Convert image v5.1 changes:

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

Convert image v5.0 changes:

Fixed issue with temp file cleanup.

Convert image v4.9 changes:

Fixed issue with try / catch code.

Convert image v4.8 changes:

Compatible XF 2.x versions: 2.3. Now supports Image optimization (WebP) function.

Convert image v4.7 changes:

Fixed issue with checking for WEBP support when using GD.

Convert image v4.6 changes:

Fixed issue with converting images in conversations.

Convert image v4.5 changes:

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

Convert image v4.4 changes:

Added 'Convert conversations' to options page.

Convert image v4.3 changes:

Added 'Exclude domains' to options page.

Convert image v4.2 changes:

Now retains IMG bbcode options.