Refactoring operation should wait for the Solr index to be empty before proceeding

Renaming a page for example will also refactor links pointing to that page, but that's only if the Solr indexer has indexed these links. An example use case is a loop where you're renaming several pages, this will trigger some reindexing and some renames may fail if the Solr indexing is in progress and hasn't finished.

Thus the idea is to introduce some new request.setWaitForIndexing(true|false), and to set it to true by default (better be safe than sorry) and allow scripts to change the behavior for the cases where it's not needed.

Note that if the wiki is being indexed (after a large XAR has been imported for example), then any refactoring operation may take a long time (the time to index). Thus any refactoring operation must be done in a job with a progress bar, and it would also be nice to indicate in refactoring UIs the solr indexing level somewhere.

This issue might need a forum proposal.