[ENH] wiki attachments modernization

• wiki attachment fixes when working in file gallery storage mode - unify with original wiki attachments, update when uploading via wiki edit page properties, show attached files count, rename page rename only attachment type file gals
• wiki attachments migration tool and admin UI updates to help with migration and different storage engines
• automatically replace img/file plugins referencing attachments with their versions referencing files when migrating to file galleries
• remove experimental tag and make fgal storage of attachments the default for new installs
• permission enforcing for files stored as wiki attachments in galleries
• edit attachments gallery types display the name and type in read-only manner
• implement wiki put mailed in wiki pages attaching files using file galleries as storage