fix brackets and names

remove some whitespaces

adjust the scope of revolve macro

revolve configuration works

use macro PETSC_HAVE_REVOLVE

remove revolve sources files from PETSc

skip the starting and ending step correctly

color output messages

Use global stepnum only in the forward sweep, not in the recomputations stage

use global stepnum, and fix error types

remove printf statements (for debug only)

fix a tiny bug

two level checkpointing works perfectly; stupid revolve!

reduce number of checkpoints (the first and last ones are removed)

refactor the code

change some names

add two-level checkpoiting, the version without revolve works

Postpone stack allocation to setup stage of tstrajectory, -tstrajectory_max_cps works now

trying to add an option -tstrajectory_max_cps

refactor the code a little bit

fix the memory access bug when creating revolve object

cleanup trailing whitespaces

forgot to add revovle source files

results verified to be correct

allow recomputing the solution when not all time steps are checkpointed in memory
for testing, the checkpoints are randomly determined