fix(uiSref): nagivate to state when url is ""
fix($state.href): generate href for state with url: ""
test(uiSref): add tests for html5Mode

Made resolve values ignore any keys that we're actively trying to resolve, when they also exist in some parent state.
Made ui-sref ignore a single preventDefault that comes from the <a> directive when there is no href (and the ui-sref is on an <a>)

Closes #1363
Merge pull request #1363 from angular-ui/issue-1362

fix(uiSref): nagivate to state when url is ""