Bypass channel cache completely in thread reloads

This solves Fx27.0a1's "NS_ERROR_CACHE_WRITE_ACCESS_DENIED (-200)" problem, which may be a bug introduced by Bug 925352.
Add async file writer to arAkahukuFile mod
Add a new option to paste&attach image from clipboard
Version sp_rev.19
Bypass channel cache completely in thread reloads

This solves Fx27.0a1's "NS_ERROR_CACHE_WRITE_ACCESS_DENIED (-200)" problem, which may be a bug introduced by Bug 925352.
Merge branch 'develop'