Refactor and porting of service explorer code.
Addressed review comments. Actions list is now disabled while a node is being loaded. Removed some unused code.
Disabled propagation of left-clicks to a node while it is in a 'loading' state.
Marked node as loading for mobile service script nodes (table scripts, custom APIs and scheduled jobs) when they are clicked to prevent them from being invoked during subsequent clicks. Added a 'Manage subscriptions' action to root 'Azure' node.
Merge pull request #66 from avranju/service-explorer-refactor

Refactor and porting of service explorer code.