This is a redo of #6432 because of merge conflicts.
Please see that one for test instructions
The problem
I discovered that the alignment on the login page of isis is not 100% pixel perfect. The field are just a few pixels to width. Hower, on RTL languages the wrong alignment was very good visible. So this patch solves alignment problems on LTR and RTL languages. I also add the possibility to load the templates-rtl.css in the login-view.
Farther optimizations:
font-set icon icon-joomla instead of .png icon for the Joomla! logo on bottom of the loginform
Full width login button
Before/after screenshots
LTR before
LTR after (very small difference on the right of the fields)
RTL before
RTL after
How to test this patch
Confirm the before/after screenshots on a LTR language (English)
Confirm 100% page width button and sharp Joomla! logo on bottom
Change your language to a RTL language (Persion for example)
Test step 2 and 3 again.
Confirm the login layout is also good shown on mobile devices. Feel free to use the Google Chrome F12 developer tools for this part
Notes
Also add some extra spaces for CS on some places
As idea of @dgt41 the login button is full-width. Please let me know how you're thoughts are about that
Merging as original PR was already RTC