70%: Multiple database connections

The main change is that all mongo connections are now delegated through MongoTripodConfig.  In order to reduce the complexity to the developer, some constraints were required: e.g. CBD collection names now have to be unique within configuration (table_rows, views, and search do not, since they're not accessed directly and MongoTripodConfig can sort things out based on the spec id).

This is a breaking change, however. TARL, for example, has CBD_config collections in both the tenant and global databases: these were differentiated by specifying the database, which is no longer workable.

Instead, this concept has been replaced by 'configSpecs'.  When you instantiate your Tripod instance, you can also specify an (optional) configuration specification for it and all of its delegates to use.  For example:

```php
$config = array(...); // Bunch of regular old Tripod configuration stuff
MongoTripodConfig::setConfig($config); // This becomes the 'default' configSpec

$otherConfig = array(...); // Configuration for another tripod instance that may conflict with the previous
MongoTripodConfig::setConfig($otherConfig, 'other');

/* This instantiates a MongoTripod with the default configuration: views, tables, 
* locks, transactions, labeller, etc. are all scoped within this configuration
*/
$tripod = new MongoTripod('CBD_example');
$tripod->getConfigSpec();

=> 'default'

$tables = $tripod->getTripodTables();
$tables->getConfigSpec();

=> 'default'

$views = $tripod->getTripodViews();
$views->getConfigSpec();

=> 'default'

// etc.

/* This instantiates a MongoTripod with the other configuration: views, tables, 
* locks, transactions, labeller, etc. are all scoped within this configuration
*/
$tripod = new MongoTripod('CBD_example', array('configSpec'=>'other'));
$tripod->getConfigSpec();

=> 'other'

$tables = $tripod->getTripodTables();
$tables->getConfigSpec();

=> 'other'

$views = $tripod->getTripodViews();
$views->getConfigSpec();

=> 'other'
```