* move the metadata descriptors to a submodule metadata
* the crate itself (not the tests) should compile with stable
  -> verify / improve handling of LOBs and of longdate
* implement other date-types
* implement geospatial types
* resolve fixmes in resultset and other important fixmes


src/protocol/authenticate.rs:144:    // FIXME the server proof is not evaluated
src/protocol/lowlevel/argument.rs:40:    // FIXME should be a separate struct:
src/protocol/lowlevel/argument.rs:42:    // FIXME should be a separate struct:
src/protocol/lowlevel/conn_core.rs:28:    // FIXME transmute into explicit structure; see also jdbc\EngineFeatures.java :
src/protocol/lowlevel/message.rs:157:            // FIXME: 2 ReplyTypes that occur only in not yet implemented calls:
src/protocol/lowlevel/message.rs:161:            // FIXME: 4 ReplyTypes where it is unclear when they occur and what to return:
src/protocol/lowlevel/part.rs:19:    pub kind: PartKind, // FIXME can we remove this?
src/protocol/lowlevel/partkind.rs:10:    TransactionId, // 11 // Transaction identifier // FIXME is missing
src/protocol/lowlevel/partkind.rs:17:    CommandInfo, // 27 // Command information // FIXME is missing
src/protocol/lowlevel/partkind.rs:18:    WriteLobRequest, // 28 // Request data of WRITELOB message // FIXME is missing
src/protocol/lowlevel/partkind.rs:20:    WriteLobReply, // 30 // Reply data of WRITELOB message // FIXME is missing
src/protocol/lowlevel/partkind.rs:21:    Parameters, // 32 // Parameter data  // FIXME is missing
src/protocol/lowlevel/partkind.rs:23:    SessionContext, // 34 // Session context information  // FIXME is missing
src/protocol/lowlevel/partkind.rs:25:    PartitionInformation, // 40 // Table partitioning information // FIXME is missing
src/protocol/lowlevel/partkind.rs:33:    FindLobRequest, // 49 // Request data of FINDLOB message // FIXME is missing
src/protocol/lowlevel/partkind.rs:34:    FindLobReply, // 50 // Reply data of FINDLOB message // FIXME is missing
src/protocol/lowlevel/partkind.rs:37:    LobFlags, // 68 // LOB flags // FIXME is missing
src/protocol/lowlevel/parts/client_info.rs:41:    #[allow(dead_code)]// FIXME (see info.txt)
src/protocol/lowlevel/parts/client_info.rs:56:#[allow(dead_code)]// FIXME (see info.txt)
src/protocol/lowlevel/parts/lob.rs:84:    // FIXME we should also have sth like into_byte_stream()
src/protocol/lowlevel/parts/lob.rs:154:    // FIXME we should also have sth like into_character_stream() with deferred chunk fetching
src/protocol/lowlevel/parts/parameters.rs:32:        let mut data_pos = 0_i32;  // FIXME or must it be 1?
src/protocol/lowlevel/parts/resultset.rs:101:    /// FIXME Should be replaced with a method get_rows() -> Iterator.
src/protocol/lowlevel/parts/resultset.rs:237:        try!(self.fetch_all());  // FIXME should be avoided
src/protocol/lowlevel/parts/resultset.rs:242:    // FIXME implement DROP as send a request of type CLOSERESULTSET in case
src/protocol/lowlevel/parts/resultset.rs:407:                // cannot happen FIXME: make this more robust
src/protocol/lowlevel/parts/resultset_metadata.rs:82:    /// FIXME is it OK that we ignore here the column_name?
src/protocol/lowlevel/parts/resultset_metadata.rs:83:    /// FIXME for large resultsets, this method will be called very often - is caching meaningful?
src/protocol/lowlevel/parts/typed_value.rs:574:            // FIXME improve error handling:
src/rs_serde/de/rs_deserializer.rs:141:        self.rs.last_row().unwrap(/* FIXME */).values.len()
src/rs_serde/de/rs_deserializer.rs:146:        self.rs.get_fieldname(idx).unwrap(/* FIXME */)
