More generic layout for caching.

- new $wgBugzillaCacheType, replaces $wgBugzillaUseCache and $wgCacheObject
  with mysql, apc, memcache, postgresql, sqlite, dummy types;
- new Bugzilla::getCacheClass() and ::getCache() static methods;
- new BugzillaCacheI::setup() abstract method, called by BugzillaCreateCache();
- new BugzillaCacheSql class, handling any generic MW SQL-backend;
  BugzillaCacheMysql is dropped;
- separate SQL CREATE TABLE definitions for MySQL, PostgreSQL and SQLite;
- base64_encode/decode cached values, fixes SQL escaping issues;
- drop cache db fetched_at column.
Fix Undefined index: bugs in BugzillaOutput.class.php on line 85

Notice: Undefined index: bugs in /var/www/wiki/mediawiki/core/extensions/mediawiki-bugzilla/BugzillaOutput.class.php on line 85

Not got the config quite right for a different MW install

I guess the constructor of BugzillaOutput should check that the returned data is halfway valid too...

        $this->query = BugzillaQuery::create($config['type'], $options, $title);

        // Bubble up any query errors
        if( $this->query->error ) {
            $this->error = $this->query->error;
        }

Also trimmed some trailing whitespace at the same time
Update pCharts to 2.1.3

Remove useless index.php as no examples folder
Merge pull request #13 from rdalverny/rework_cache

More generic layout for caching.
Merge pull request #21 from reedy/bugsundefinedindex

Fix Undefined index: bugs in BugzillaOutput.class.php on line 85
Remove .DS_Store
Merge pull request #25 from reedy/pcharts213

Update pCharts to 2.1.3