Added option to set polarion-group-id property for test-runs

[ntkathole]

# betelgeuse test-run --help | grep test-run-group-id
 --test-run-group-id TEXT        Test Run GROUP ID to be created/updated.

# betelgeuse test-run --test-run-id "abc" --test-run-group-id "groupID" --custom-fields isautomated=true --custom-fields arch=x8664 --custom-fields variant=server abc.xml /tests/foreman/ rhsat6 RHSAT xyz.xml

<testsuites>
    <properties>
         <property name="polarion-group-id" value="groupID" />
    </properties>
    <testsuite>
         <testcase>
         </testcase>
    </testsuite>
</testsuites>

[codecov[bot]]

Codecov Report

Merging #125 into master will increase coverage by 0.07%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #125      +/-   ##
==========================================
+ Coverage   88.65%   88.72%   +0.07%     
==========================================
  Files           5        5              
  Lines         476      479       +3     
==========================================
+ Hits          422      425       +3     
  Misses         54       54

Impacted Files	Coverage Δ
betelgeuse/__init__.py	87% <100%> (+0.14%)	:arrow_up:

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[ntkathole]

@elyezer Updated. Thanks!