Add preconditions to invoke WFS 2.0 from DGIWG WFS profile

[rjmartell]

The latest revision of the DGIWG WFS 2.0 profile (DGIWG 122, 16 Nov 2015) is based on the WFS 2.0.2 specification (OGC 09-025r2).

There should be a precondition to check that the IUT implements WFS 2.0.2. If not, all remaining tests are skipped.

[rjmartell]

Defining preconditions as actual test methods in a separate conformance class is preferred, since this makes them much more visible in the report so it's obvious if one fails.

For example, see the org.opengis.cite.iso19142.SuitePreconditions class in the WFS test suite.This class is referenced in the TestNG configuration file as the only member of the "Preconditions" conformance class:

<test name="Preconditions">
  <classes>
    <class name="org.opengis.cite.iso19142.SuitePreconditions"/>
  </classes>
</test>

[dstenger]

We are currently fixing this issue.

[dstenger]

In the last meeting we decided to implement this check in a single test to prevent failure of the whole test suite when WFS 2.0.0 is used.

[dstenger]

A test for WFS 2.0.2 was implemented in pull request #6 (more information in the pr).

The pull request has already been merged to the master branch.