Leading _kset_ to _kset_ join operator fails to parse in DSL

[jonathan-beard]

Describe the bug

The following line of code:

 m += ( raft::kset( g0, g1, g2 ) >> raft::kset( a, b, c ) ) >= ( j >> print );

should parse according to the grammar, indeed there is a test case in the dev branch to
ensure that this is the case. Syntax, however, fails to parse in the master branch.

To fix, pull test cases to master branch, and debug from there.

Steps To Reproduce

Run test case ksetContContJoin.cpp

Expected behavior

• M producers in first kset should be joined to M consumers in second kset

[jonathan-beard]

Started new branch, will tag when I have some commits for this issue specifically.