Add case insensitive checks for token addresses in collectibles and tokens controllers

[adonesky1]

This seeks to resolve a host of issues that can arise when token addresses with different casing slip through.

[ryanml]

++ - we have this pattern (one of comparing two addresses by lower casing them both) in a lot of places throughout the codebase, it may be nice as a followup to write a helper for this (ex addressesAreEqual(a1, a2)) just for general DRY purposes. May be overkill, just a thought!

[Gudahtt]

Even better would be to perform input validation to guarantee they're always cased predictably (with accompanying state migrations on each product)! Probably best to use check-summed addresses, as per EIP-55. But that's a huge task.

[adonesky1]

Even better would be to perform input validation to guarantee they're always cased predictably (with accompanying state >migrations on each product)! Probably best to use check-summed addresses, as per EIP-55. But that's a huge task.

Agreed. This was a short term patch that affords us some guarantees until we can do that bigger chunk of work.