Enable PCPs on events

The attached patch file allows for events have PCPs attach and reference them.

It is tested in our production environment and has only one known issue; when on the manage events page, clicking on a configure link and then the subsequent PCP link does not load the correct information. Clicking on any other link within the configure menu (eg. info and settings) and then navigating via the PCP tab does work.

The following table alterations are required and are not part of the patch:

ALTER TABLE civicrm_pcp_block DROP FOREIGN KEY FK_civicrm_pcp_block_entity_id;
ALTER TABLE civicrm_pcp DROP FOREIGN KEY FK_civicrm_pcp_contribution_page_id;
ALTER TABLE `civicrm_pcp` ADD `page_type` VARCHAR( 64 ) NOT NULL AFTER `contribution_page_id`;
ALTER TABLE `civicrm_pcp` CHANGE `page_type` `page_type` VARCHAR( 64 ) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL DEFAULT 'contribute';
ALTER TABLE `civicrm_pcp` CHANGE `contribution_page_id` `page_id` INT( 10 ) UNSIGNED NOT NULL COMMENT 'The Page which triggered this pcp';
UPDATE `civicrm_pcp` SET page_type = 'contribute' WHERE page_type = '' OR page_type IS NULL;