[cli-clean] expanded interface, will need in smoke, possibly harness
[cli-clean] clean accepts directories
[cli-clean] clean accepts a list
[cli-clean] added verbose option
[cli-clean] comments and whitespace
[cli-clean] added ~dir for harness, smoke, etc to use
[cli-clean] made directory optional
Merge pull request #78 from cs3110/cli-clean

cli-clean: clean directories, accept list of targets