revisions after reviews

Hello SciPy 2012 Program Committee Members,

I made several improvements based on the reviewers’ suggestions, including:

related work: added new section (w/ several new references) on background + timeline on other mesh-based visualization tools that leverage python

why python for VisIt?: added brief info on the reasons python was selected for scripting by the VisIt team in 2001

client interface API details: details about VisIt’s C++ RPC infrastructure and why the client API is procedural / modal

general: fixed some grammar issues, simplified verbiage in a few sections, used the abbreviation “CLI” more consistently

-Cyrus