Change command error stream prefix to STDERR.

Currently output written to stderr by a process shows up in the console
log with the prefix "ERROR: ". This can cause the user to interpret all
messages written to stderr as errors and many are just informational.
This change will help users make this distinction.
Merge pull request #688 from mmb/stderr-output-prefix

Change command error stream prefix to STDERR.
Version bump up - 14.4.0
* Haven't bumped up versions in curl.task.plugin and sample-plugin.descriptorHash plugin XMLs. These will be updated as part of the sample plugin migration to messaged based plugins.
Merge pull request #740 from mdaliejaz/versionBumpUp

Version bump up - 14.4.0
Merge pull request #743 from pshivana/migrate_package_repository_extension

#738 Fixed issues