Enabled the new trial type "rest" in expt_config.txt -->
TRIAL_TYPES_IN_BLOCK.

This is the no-speech resting trial type, mainly for fMRI experiments.
Note that the visual display during the rest trials will be drawn
randomly from the field STIM_REST, also newly added.

The new fields are added to the two example expt_config files.

	modified:   mcode/expt_config.example_fmri.txt
	modified:   mcode/expt_config.example_pitch.txt
	modified:   mcode/genRandScript.m
	modified:   mcode/read_parse_expt_config.m
	modified:   mcode/runExperiment.m
Merge branch 'nwu' of https://github.com/shanqing-cai/ape_pitch into nwu