Create ElasticSearch index if absent; add test suite utilities

And move object FullTextSearchIndexer downwards, to below the related class.
Have an Akka actor index posts

This'll work better later when reindexing old stuff — the actor will be able to
throttle indexing speed, which is required when running on an Amazon EC2 micro
instance.

Move-rename fullTextSearchIndexPost() and makeSearchEngineJsonFor() to
IndexingActor.
Add column DW1_PAGE_ACTIONS.INDEX_VERSION.
Background-index posts, remember which have been indexed

Implement functions like:
- findPostsNotYetIndexed
- rememberPostsAreIndexed(inidex-version, page-and-post-ids)
And have the IndexingActor load and index posts-not-yet-indexed.

Also:
- Have the test suite delete the index before running tests
- Test that posts are reindexed in the background; add debugUnindexPost()
- Give a RelDbDaoFactory to the site and system DAOs.
- Make batchLoadAncestorIdsParentFirst() work with many page ids
- Add unimplemented but mostly working loadPostStatesById()
- Rename some things
Close ElasticSearch before stopping the IndexingActor.
Rename package com.debiki.v0 to com.debiki.dao.rdb

And other parts of com.debiki.v0 were renamed to .core and .tck.dao.
Delete project build file

Build config is specified in parent project debiki-server actually.
Rename RelDb[Tenant/System]DbDao to Rdb[Site/System]Dao

Plus some other renames.
Rename things from RelDb to Rdb.
Rename "tenant" to "site" here and there, e.g. tenantId to siteId.
Check that daoFactory.isTest before calling emptyDatabase().
Fix comment: Change "RelDbTenantDao" to "RdbSiteDao".
When running tests, create index synchronously

Otherwise apparently debugDeleteIndexAndMappings() fails to *delete* it, no
idea why.

Also log more messages.
Have trait FullTextSearchSiteDaoMixin extend SiteDbDao

This makes IDEA's navigate-from-function-declaration-to-implementation work.
Strip HTML stuff when indexing text.
Fix search engine tests: Always create index synchronously

Otherwise search engine test fails: changes to the index has no effect, if it's
created asynchronously when instantiating the RdbDaoFactory, then deleted and
created again. Don't know why the recreation has no effect: the original index
apparently remains unchanged.