Enable JSHint's `quotmark` rule.
Merge pull request #484 from XhmikosR/quotmark

Enable JSHint's `quotmark` rule.
Enable JSHint's `eqeqeq` rule and remove `eqnull`.
Move global config to JSHint's configuration.
Remove unused variables.
Enable strict mode.
Fix test failures after the strict comparison changes.
Fix typo.
testrunner.htm: fix undefined variables.
Enable JSHint's `camelcase` rule.