#727 package repository extension now supports message based plugin API
#727 handled plugin type and null configurations in metadata loader and modified json format for ease of use at plugin side
#727 Removed plugin id from GoPluginIdentifier, added javadocs plugin api classes and added apache license header
Merge pull request #728 from pshivana/migrate_package_repository_extension

#727 package repository extension now supports message based plugin API
#727 Fixed failing test
Merge pull request #737 from pshivana/migrate_package_repository_extension

#727 Fixed failing test
Introduced stub package definition service to fixed package_controller_spec and admin pipelines_controller_spec failing. PackageMaterialMetadataLoader modified to listen to plugin change events for GoPlugin class. JsonBasedPackageRepositoryExtension handles empty response for latest modification since call.
Merge pull request #738 from pshivana/migrate_package_repository_extension

Fixing issues with Json based plugin api for package repo.
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
#718 - Introduced TaskExtension which acts as adapter to channel API and Message/json based tasks. ApiBasedTaskExtension handles all requests for old-styled task apis. Yet to implement Messagebased extension methids
#718 - implemented json-based task extension. fixed task-metadata-loader to delegate to appropriate extensions to load and cache the metadata
#718 - extracted out task extension handler for version 1.0. Each handler is registered with the jsonBasedTaskExtension. appropriate handler is invoked based on the version implemented by the plugin
#718 - Changed the json format of task config. passing config, environment vars, working dir and console as part of request to plugin
#718 - Fixed failing tests. modified tests to use mock instead of stub
#718 - PluggableTaskService invokes validate through task extension. Changed json format for validation error
#718 - Created a ConsoleWrapper to be used by json based plugins. ConsoleForJsonBasedPlugin will be passed on in the request instead of the Console directly
#718 - defined taskentension as a bean on agent so we dont have to serialize it across. fixed few bugs for this story