Investigate possibility to use sqlite for mail indexing/storing

Phenomenon

Currently YAM saves each mail in a separate file using an index file to quickly find mail throughout the filesystem. It might be, however, a better approach to use perhaps an SQL based approach (e.g. using 'sqlite').

Background analysis

On AmiNET there exists an amiga port of sqlite 3.6.1 (​http://aminet.net/package/biz/dbase/sqlite-3.6.1-amiga) which might be a good basis for a test.

Implementation recommendation

A prototype have to be created where several thousands emails should be stored and indexed in a basic SQL database using sqlite. Performance tests against the current solution should be made and based on these performance tests the prototype should be converted into code usable for YAM (or not).