Improve memory usage

[jumpinjackie]

We seem to be allocating objects with reckless abandon to the point where node errors with ELIFECYCLE (ie. out of memory) when we try to generate a d.ts for Cesium.js

[jumpinjackie]

Initial plan of attack:

• Add memory debugging facilities (node-memwatch)
• Profile run against ol3 source
• Remove the use of various classes in tsoutput.ts. These classes are nothing more than intermediate objects about the original JSDoc doclet. While convenient, I strongly believe the bulk of the memory usage is in storing these objects all over the place. Replace with utility methods that do the same thing off of the original doclets.
• Re-profile run against ol3 source

[jumpinjackie]

Downgrading severity. ELIFECYCLE is not due to OOM, but because JSDoc actually reported errors.

That's not to say we can't improve the memory usage, but it doesn't appear to be the cause at the moment