Merge pull request #136 from dkocher/master

HMAC-SHA2, PuTTY key format, concurrent read for downloads and bug fixes
support multiline password prompts #132
Change CONTRIBUTORS to contain the relevant command for getting at this info
not handed over yet
don't close underlying RemoteFile when closing streams of that file - reverts f34667521d4c82fbfc2588c74972ad4d6d0e6e45
some small tweaks to PKCS8KeyFile in relation to the PEMReader -> PEMParser transition
get rid of over-zealous sending of channel EOF & close messages which was implemented with questionable synchronization

fixes #105

also relevant to #126 since AbstractChannel does not synchronize on
'this' anymore
no biggie if we don't send EOF on ChannelOutputStream.close()
StreamCopier logging
Read-ahead input stream moved to its own class, as it will not play nice with mark/reset/skip. Use it by defautl for SFTPFileTransfer.

Closes #76 - no longer a significant difference in scp & sftp transfer speed
consistent license headers using plugin
next release will be 0.10.0
release plugin mgmt
restore accidently removed assembly plugin for examples jar
onwards to 0.10.1-SNAPSHOT