Modify mobility of agents during tpre time period

[godisreal]

It is important to modify mobility of agents during tpre time period. Otherwise agents before tpre (in pre-evacuation stage) will block others' way in the simulation result.

In order to solve this problem TPRE_TAU and TPRE_TAU_INER are added in PERS namelist so that agents can move around during tpre time period so that they will not block others' way. Please refer to color4test44.zip for detailed result.

Below is the discussion about this feature in FDS google forum. Thanks Timo for guidance.
https://groups.google.com/forum/?fromgroups#!searchin/fds-smv/tpre%7Csort:date/fds-smv/qNAbpZ8Y2-A/m4DT7Vh2BgAJ