Create a cache system (sqlite+.gz files) for all views

Proposed solution for issue #159 

### glossaire.sh
Store UNIX timestamp of last run for cache invalidation.

### classes/CacheViews
Class to manage sqlite database and cache entries

### classes/Json
Added parameter to encode or just print received data, perform simple output or full output (with headers).

### Views
Modified to not use $locale as a local variable and not die after using Json::output

### contants.php
Added NOCACHE to always served non cached views

### dispatcher.php
Cache management, don't use template for showrepos+json