Request: Add configure option for 24h clock

[Reinis]

Currently sunrise/sunset times are given in 12h clock with am/pm attached. It would be nice to set it to use 24h clock where am/pm are not needed.

[Reinis]

Maybe also add a choice to use system setting for this, then the clock in the weather applet always will be consistent with the clock applet.

[Odysseus86]

This fork by me does what you're asking.
I've submitted a pull request to simon04, so that hopefully he integrates my changes into his own branch.