Pull requests related to cartridge building

* Enabled connection hooks for non-scalable apps. Allows for plugin cartridges to pass information to frameworks.
* Enable connection hooks to return messages back to user (must be type starting with INFO:). Allows plugin cartridges to print messages to user based on type of framework installed without hardcoding logic to detect cartridge type.
* Added REST API endpoints to add/remove/list user provided environment variables.
* Extend PHP cartridge to use additional PEAR packages and include files specified by plugin cartridge