GetDouble and GetFloat less type auto conversion

[dczuo]

simple example:
using (var reader = new MySqlCommand("select 1 / 3 from tablename", conn).ExecuteReader())
{
reader.Read();
reader.GetDouble(0); // InvalidCastException
reader.GetFloat(0); // InvalidCastException
}

[bgrainger]

MySqlConnector currently only performs a small number of known "safe" conversions; see #481 and #406.

Note that a decimal column can be retrieved as an int (#54) so it may make sense to allow implicit conversion to float/double (which would be less lossy).

Like similar issues, this needs testing in AdoNetApiTest first.

[bgrainger]

Added to AdoNetApiTest: mysql-net/AdoNetApiTest@2a48acc

Conversions from a decimal column (or implicit decimal result) will be handled automatically by GetDouble and GetFloat.

[bgrainger]

Fix shipped in 0.57.0-rc1.

[dczuo]

thanks