Performance fixes

Here's two firefox performance profiles comparing a before & after of what I've done so far for this:

baseline.json

after_changes.json

And here's the two flame charts:

Baseline:

After the changes:

Changes:

• Debounced ng-model updates by 100-500ms
• Added track bys to almost every ng-repeat directive
• Stopped using a very frequently called function, isUniqueTableable(), because nothing was actually using the function's output
• Memoized other very frequently called functions - tableables() and getFieldType()

Fixes #488 (closed)