increase rate at which tox_do() is called

file transfers need tox_do() to be called often to reach high speeds
fix multiple file transfers

FileTransfer .filenumber was not being set
fixed file transfers for multiple friends

file transfer ids are per friend, not global
added resuming file transfers

-only works with disconnects (and not client restarts)
only set file transfer to broken if it was in progress
sending file data without reading/writing to file

-automatically accepts .png files <=1MiB as data
sending clipboard as png
displaying received png in chat

-missing option to "Save As" the images
accept and display jpg images too

-send clipboard as jpg if png of clipboard >1MiB
-images aligned to left in chat now
show progress when recieving data
Merge branch 'working' of github.com:notsecure/Venom into notsecure-working
Merge branch 'notsecure-working'