CRM-14439 - CRM_Core_Invoke::rebuildMenuAndCaches - Change order

Currently, CRM_Core_Menu::store() truncates "civicrm_menu" and then refills
it; then, CRM_Core_Config::clearCaches (by-way-of clearDBCache) truncates
"civicrm_menu" without refilling.  This seems pointless.  (For CRM-14439,
this has the effect of producing an empty menu table after running setup.sh
-- so the table is eventually filled at some uncontrolled future point.)

The evident intent of "rebuildMenuAndCaches" is to truncate and then refill
the table, so this patch does that.

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* CRM-14439: WP demo - Access denied when visiting breadcrumb links from field listing
  https://issues.civicrm.org/jira/browse/CRM-14439
Merge pull request #2858 from totten/4.4-wp-breadcrumb-cacheclear

CRM-14439 - Fix WP breadcrumbs by forcibly pre-computing them with "wp-admin/admin.php"