ENH: ignore size specification for numeric types

ENH: TIME can be specified a size with PGSQL
BUG: no size for usual numeric types with PGSQL

     specification in the form of a double instead of a singleton), but for
     now size is ignored for FLOAT and DOUBLE types with  MySQL.

     strings that are constructed with mixed string and integer types.

COMP: Move private implementation details out of vtkMySQLDatabase and into a PIMPL class, to eliminate errors compiling client-server wrappers.

     using += operator... use ostringstream.

     a case statement.
ENH: use vktStdString() instead of 0 for a really empty vtkStdString.

STYLE:Be more accurate about viewport coordinates. The range of coordinates [-1,+1],[-1,+1],[nearz,farz] is for points located inside the frustum.