Console command to find blocks

[nadar]

Add new command in order to find blocks by its name and display how many times they are used inside the contents. This can be part of a migration to in order to rename class names.

/**
 * Usage:
 * 
 * ```
 * ./luya cms/block/find
 * ```
 * 
 * Filter for a given name:
 * 
 * ```
 * ./luya cms/block/find html
 * ```
 * 
 * Filter for different names combined as OR conditions:
 * 
 * ```
 * ./luya cms/block/find html,module
 * ```
 */