[DB MIGRATION REQ'D] Fix count history indexes
Fix bug where multi-column indexes caused inconsistent query results
Clean up tests, standardize milestone threshold to 20
Correct migration (remove rollback, fix type insertion)
Fix case in file paths
Favorited Links Insight
Closes #1615, closes #1665
[DB MIGRATION REQ'D] Fix Twitter crawler bug that didn't set in_reply_to_user_id
Migration backfills existing rows with incomplete data
Speed up migration; use in_reply_to_user_id_str
Only run new SQL without version numbers in the files when upgrading --with-new-sql
Fix upgrade.php --with-new-sql failures on source with database migrations

Prior to this commit, when a developer pulled the source code and there was a database migration since the last stable release, php upgrade --with-new-sql potentially failed because that migration was already published in build-db_mysql.sql, which was already run during installation.

This commit reverts build-db_mysql.sql to the latest version release, and creates a new script, build-db_mysql-upcoming-release.sql, which tests use. When the developer installs from source, s/he must also then run php upgrade --with-new-sql afterward, which will apply any pending migrations which have not gone out in a new user release.

From now on, when a new user release gets packaged up, every change in the upcoming-release sql script will get rolled into build-db_mysql.sql.