Treat frequencies in bookmarks as 'LongLong' (qint64)

Fixes issue #192
QT doesn't need svg

It looks like QT doesn't need svg here.  This causes the binary to attempt linking to qtsvg, however, since gqrx doesn't actually use qtsvg, this seems kinda silly.

the downstream bug is here:
https://bugs.gentoo.org/show_bug.cgi?id=521206

Are we missing something?
Merge pull request #195 from ZeroChaos/patch-1

QT doesn't need svg
Update readme with required Qt components
Allow fractional ppm correction

0.1ppm should be enough for anybody... O:-)

But seriously, both my hackrf and rtlsdr are something like X.4-X.6 ppm and
I really want my waterfall display to line up with my reference frequency.
take credit for my li'l diff
restore ppm correction from config
Merge pull request #201 from ckuethe/master

Allow fractional ppm correction.
Merge pull request #193 from mrenouf/master

Read bookmarked frequencies as int64
Merge pull request #1 from csete/master

Merge changes from csete