Merge pull request #762 from chrox/master

add custom screen DPI option
Minor tweaks to the Kindle startup script.

Don't sleep during eips calls in ASAP mode
Only show the 'starting KOReader' eips msg w/ KUAL
Add some breathing room to the FM icons.

In the form of a spacer icon between the first/last icon and the
next/prev one. Should help with fatfingeritis.
Run every PNG icons through optipng

Very, very minor space savings ;p.
Tweak the spacer appearance condition

Make it sync with the first/last icon, instead of always showing it.
Doesn't change much, since it's invisible, but, still, more correct this
way ;).
Merge pull request #764 from NiLuJe/master

A bunch of minor tweaks
move screen DPI and refresh rate entries into Screen menu
fix #765
display OTA update menu only on Kindle and Kobo
add OTA settings for server mirrors and channels
reorder setting entries in reader menu
update pot file