Add run speed and modification of it

Run speed is somewhat interesting additional stat to movement information.

By default it's 4 times your speed, but heavy load reduces it to 3 times. Run feat increases it to 5 times.

Exhausted and fatigued disables running (run speed set to 0, effectively).

There's various traits that increase Only run and charge speed similar to Fleet feat, such as one of the alternate racial traits for tieflings.

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Charge and Withdraw speeds could similarly be included, since they have similar modifiers.