PHP APC configurable per gear size / env var

- APC is enabled by default
- Users can enable/disable APC by running
  `rhc env-set OPENSHIFT_PHP_APC_ENABLED=false --app <app>`
  and `rhc app-restart <app>` commands

APC shared memory size:
- Formula: GEAR_MEMORY/8
  - 64M on Small gears by default
  - 128M on Medium gears by default
  - 256M on Large gears by default
- Users can change the APC shared memory size by running
  `rhc env-set OPENSHIFT_PHP_APC_SHM_SIZE=128M --app <app>`
  and `rhc app-restart <app>` commands

New environment variables:
- $OPENSHIFT_PHP_APC_ENABLED=true/false
- $OPENSHIFT_PHP_APC_SHM_SIZE={64,128,256}M
PHP - Development/Production mode

- Expose new environment variable to choose application mode:
  APPLICATION_ENV=development/production (production by default)

- Users must restart their app for the PHP to pick-up the updated values!

Production environment:
- disables Xdebug (can be overriden by `OPENSHIFT_PHP_XDEBUG_ENABLED=true`)
- disables APC stats (for better performance)
- sets error_reporting level to `E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR|E_PARSE`
- disables display_errors, display_startup_errors, track_errors, html_errors

Development environment:
- enables Xdebug (can be overriden by `OPENSHIFT_PHP_XDEBUG_ENABLED=false`)
- sets Xdebug max_nesting_level = 200
- enables APC stats
- sets error_reporting level to `E_ALL|E_STRICT`
- enables display_errors, display_startup_errors, track_errors, html_errors
Fix php file permissions cucumber tests