Changes to plugin save and load

Made use of ConcurrentHashMap explicit in PluginManager.java.
Avoided loadAll when saving a new plugin.
Completed the feedback loop to the ui on updating a configuration.
Added plugin parameter types

Added plugin parameter types.
Changed crawljax-version in plugin-descriptor.xml to list.
plugin-descriptor xml schema reference
Merge pull request #303 from crawljax/web-ui-plugin-fixes

Changes to plugin save and load
Merge pull request #304 from crawljax/web-ui-plugin-params

Added parameter types.
Merge remote-tracking branch 'origin/web-ui-plugin-support' into feature/web-plugin-deployment

Conflicts:
	web/src/main/java/com/crawljax/web/fs/PluginManager.java
	web/src/main/java/com/crawljax/web/model/Plugin.java