Support for reading AMBER mdcrd trajectories

[badarsh2]

Re-request of PR #287 created earlier.
I messed up with the previous PR while rebasing, so I've created one afresh.

Approach: Since the mdcrd datatype is merely a huge sequence of floats, I'm initially reading them an storing them in the molecule class as a coordinate set. Then I invoke the custom gui dialog here in mainwindow which gets the numAtoms from the user. Appropriately, the atoms are then added, and the scene is set.

Though the implementation not quite elegant, it does the required job straightforwardly. Suggestions for improvements are welcome.

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Signed-off-by: Adarsh Balasubramanian badarsh2@gmail.com

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[cryos]

This seems to have unrelated changes adding a molecule information dialog. It would be good to separate that out.

[ghutchis]

@cryos - the dialog seems related to resolving the mdcrd trajectories - which I think just include coordinates, not atom/bond assignments.

This is old, but I'm okay merging.