Add header/legend line to kp_reader

[brian-kelley]

Add header line to kp_reader describing what each column means.

For example:

[bmkelle@s1042556 unit_test]$ ~/kp_reader s1042556-55120.dat
 (Type)   Total Time, Call Count, Avg. Time per Call, %Total Time in Kernels, %Total Program Time
-------------------------------------------------------------------------

Regions: 


-------------------------------------------------------------------------
Kernels: 

- KokkosKernels::Common::SymmetrizeGraphSymbolicHashMap::S1
 (ParFor)   0.986542 14 0.070467 24.654143 12.271012
- KokkosKernels::Common::SymmetrizeGraphSymbolicHashMap::S0
 (ParFor)   0.977042 14 0.069789 24.416739 12.152850
...

Note, I didn't try to space this out differently with --fixed-width 1 because the columns containing numbers tend to be narrower than the corresponding header entry.