Fixed up unit test

Hopefully this will fix failing test.
Added execute bit to some EXEs
Use NpgsqlException for backend errors only

- We now throw NpgsqlException only in case of a backend-generated
  issue, as per the DbException/SqlException specs.
- #330
Merge pull request #344 from roji/npgsql_exception

Use NpgsqlException for backend errors only
Updated NpgsqlException docs for clarity
[Ignore] troublesome test

Since commit e87dcc1b1498a2e0303d1b55c434aa1dae678a23 this test fails
on the build server, but not always. Ignoring for now.
Minor work on SSL

- Added IsSecure property to allow the user to know whether we're using
  SSL
- Minor cleanup
Basis SSL test

- #291
Inconclusive tests treated as failures at build server

Some tests can return as inconclusive, e.g. SSL wasn't enabled at the
backend so the test effectively couldn't be run.

We don't want to bother developers who haven't set up Postgresql to
support everything - so inconclusive is very similar to ignore. However,
on the build server we want inconclusive tests to show up as failures,
otherwise we may miss regressions because of misconfiguration.
Removed extra_float_digits setting

No longer set extra_float_digits upon connection, let the
user manage this as they see fit.

Fixes #324