Updated DataChannelAuthentication methods and third party active modes. 
- Added methods to disable DCAU. 
- Active (3rd party) transfer mode between servers can now be reversed.
Added logger info statement.
Fixed active/passive mode bug: 
When performing passive() on source server, target server must use port
number from source server's passive() method and not use
setLocalPassive() method.
Cleanup: do not superfluous setLocalPassive() on target server!.
Changed usePassive property to useActive. 
Update comments + property descriptions.
Comments,exceptions,logging,etc.
Merge branch 'develop' of github.com:NLeSC/Xenon into feature/gftp-3rdparty-copy
Added check for null argument.
Formatting + comments.
Moved third party transfer methods to GftpThirdPartyTransfer class. 
Added support for extended mode partial third party transfers.
Changed dispose into close method.
Formatting.
Fixed weird line break.
typos
Fixed '&&' vs '&' in boolean statement. 
+ Comments and formatting.
Merge pull request #205 from NLeSC/feature/gftp-3rdparty-copy

Finished GftpSession API for 3rd party file transfer
Changed warning about non existing certificate directory to debug level.
Moved static Globus methods from GftpUtil to GlobusUtil. 
Default CA certificates only need to be (re)loaded when the actual proxy
is created.
Removed actual (re)load of the certificates during initialization.
Merge branch 'feature/gftp-3rdparty-copy' of github.com:NLeSC/Xenon into feature/gftp-3rdparty-copy
Merge pull request #209 from NLeSC/feature/gftp-3rdparty-copy

Fixed unnecessary warning, and updated static initialization methods.