create a shared/video_handler concern, now channels accept videos like projects

instead duplicate code, we moved the logic to a new
shared/video_handler concern that can be used by project and channel.
added video_embed_url into channels
channel observer to get the embed_video_url from VideoInfo
show up the video_embed_url into iframe tag now we not need to put the embed code in profile/edit
for some reason we need to use channel.reload to prevent stack level deep :/
Merge pull request #531 from devton/video_url_channel

Channel can receive a video url [Fix #62472560]