KolabMailInfoDb: Folder summary lookup from SQLite DB, various fixes
KolabMailInfoDb: Folder summary lookup from SQLite DB, various fixes

* lookup KolabFolderSummary from SQLite DB
* check for folder existence via SQLite DB
* removed ticks around column names in SQL query strings
* updated to kolab-util-sqlite API change

GNOME/evolution-kolab,GNOME/evolution-kolab