Moved exercises into subfolders of the corresponding topics

Moved exercises into subfolders of the corresponding topics

W. Trevor King: I dropped everything from the original 39e0701 except
for the python/sw_engineering/argparse_exercise.md rename.

Conflicts:
	python/data_structures/exercises/setdict.markdown
	python/data_structures/exercises/setdict_dependencies.txt
	python/intro/exercises/python.markdown
	python/obj_orientation/exercises/oop.markdown
	python/obj_orientation/exercises/oop_sushi.txt
	python/regexp/exercises/regexp.markdown
	python/testing/exercises/test.markdown
	shell/exercises/1000gp.vcf
	shell/exercises/shell.markdown
	spreadsheets/exercises/spreadsheets.markdown
	spreadsheets/exercises/spreadsheets_ex1.xls
	spreadsheets/exercises/spreadsheets_ex2.xls
	spreadsheets/exercises/spreadsheets_ex3.xls
	sql/exercises/aggregation.markdown
	sql/exercises/experiments.sqlite
	sql/exercises/experiments_null.sqlite
	sql/exercises/experiments_subqueries.sqlite
	sql/exercises/filter.markdown
	sql/exercises/intro.markdown
	sql/exercises/join.markdown
	sql/exercises/nobel_prizes.sqlite
	sql/exercises/null.markdown
	sql/exercises/select.markdown
	sql/exercises/sort.markdown
	sql/exercises/subqueries.markdown
	version-control/svn/exercises/exercise_4.cgi
	version-control/svn/exercises/planets.txt
	version-control/svn/exercises/svn.markdown
	version-control/svn/exercises/temperature.txt