feat(database): Check for Postgresql's superuser priv and pg_trgm extension (refs #4498)
feat(database): Create pg_trgm extension in database (refs #4498)
feat(database): Upgrade docread's title index with gin+pg_trgm (refs #4498)
feat(database): Add gin+pg_trgm index on document's title (refs #4498)
feat(database): Drop doc_title%d indexes and rename doc_(name|initid|profid)%d indexes (refs #4498)
feat(database): Remove FDL:FDL_FULLIDX parameter (refs #4499)
feat(database): Check for Postgresql's unaccent extension (refs #4501)
feat(database): Create unaccent extension in database (refs #4501)
feat(database): Add search.french TEXT SEARCH CONFIGURATION with unaccent support (refs #4501)
feat(database): Use search.french ts config instead of default french (refs #4501)
feat(database): Remove rewriting of highlight/headline for accentuated words (refs #4501)
feat(database): Add tests for accentuated fulltext searches (refs #4501)
feat(database): Do not check and require SUPERUSER privilege (refs #4501)

Do not check and require SUPERUSER privilege if the extensions are
already created in the database.

Required extensions can be pre-created by Postgresql's DBA, or
automatically created at install/upgrade time if the database user has
the SUPERUSER privilege.
Merge pull request #1074 from eguaj/3.3

feat(database): Use Postgresql's pg_trgm and unaccent extensions (closes #4498)(closes #4499)(closes #4501)