Fix iOS id

Selector override must happen outside the doFind function. If it's left inside
doFind, then waitForCondition will cause selector to be undefined.
Merge pull request #1129 from bootstraponline/ios_id

Fix iOS id
Expanded capabilities documentation for mobile after reviewing appium.js code.
Made explicit that `app` capability is not required to launch pre-installed Android apps.
Merge pull request #1133 from filmaj/caps-docs

Expanded capability documentation
Fix doc format
fix sauce driverblock