[Enhancement] Ranked talents should only show up in higher tiers if bought at lower tiers

[ShaneK]

Currently, all talents less than or equal the current tier are showing up when you go to select a talent.
We should filter this down to only show talents available for the current tier, taking into account ranked talents that you bought at previous tiers.

For example:
Grit shouldn't show up when you go to buy Tier 2 unless you've bought it at Tier 1 already. Similarly, it shouldn't show up in Tier 3 unless you've bought it in Tier 2. Etc.

Non-ranked talents should never show up in tiers higher than the current tier.

This will greatly reduce the clutter of going to buy a talent and more accurately reflect your choices.