Add parsing for "Your speed is unaffected by Slows"

[RealWhimsy]

Fixes part of #190

Description of the problem being solved:

This adds parsing for "Your speed is unaffected by Slows" modifiers, such as on Pathfinder's "Relentless Pursuit" notable or the unique "Wanderlust" boots.

Steps taken to verify a working solution:

• Restarted PoB with rebuilt ModCache
• Lines in "Relentless Pursuit" and "Wanderlust" now parse correctly (blue)
• Added an Attack (Molten Blast) to my Character and noted default Attack Rate: 1.26
• Attack Rate when "Are you chilled?" is active drops to 1.13
• Allocating "Relentless Pursuit" bounces the attack rate back to 1.26, ignoring the slow of the chill

Link to a build that showcases this PR:

https://pobb.in/uP9iiR1OtT2i

Before screenshot:

After screenshot:

[RealWhimsy]

Initially I implemented this as "your action speed cannot be modified to below base value", which is not correct. This way a 30% speed increase and a 20% speed decrease would result in a net 10% speed increase.

However, since our speed is unaffected by slows, it should ignore the 20% speed decrease and result in an overall 30% speed increase. I added a second commit that correctly introduces this behavior.

Implementation was briefly talked about on Discord with @Wires77 and @PJacek

Example config:

With Relentless Pursuit:

Without Relentless Pursuit: