Fix: Double Quotes in Site Name not escaped in admin section (isis templ...

...ate)

kudos goes to @dgt41 see: https://github.com/joomla/joomla-cms/issues/4864#issuecomment-59771496

#### Steps to reproduce the issue

Site Name: **Site "One" foo**
Open admin section using isis template

#### Expected result
HTML for preview button in the upper right corner:
a class="brand hidden-desktop hidden-tablet" href="http://www.my-site.com/" title="Preview Site &_quot_;One&_quot_; foo" target="_blank">Site &_quot_;One...

(without underscores around quot word)
#### Actual result

HTML not valid:
a class="brand hidden-desktop hidden-tablet" href="http://www.my-site.com/" title="Preview Site "One" foo" target="_blank">Site "One...


#### System information (as much as possible)

isis template

#### Additional comments
see: http://issues.joomla.org/tracker/joomla-cms/4864 @pl71 's issue