Hl signal integration

I have added Hl main and distant signals to the signal style. The rules are as following. 

Signal icon shows the signal which is the most powerful signal the signal can show (Hl 1 is not used because it used for Hl block signal icons which have only two lights). For example, if the signal can display Hl 2 (100 km/h), Hl2 icon is being used. If the signal's fasted signal is Hl3a (40 km/h) Hl3a icon is used.

All Hl distant signals are rendered as Hl 1 icon (with additional Ne 2 "Vorsignaltafel" embedded). I hope that Ne 2 is not too small.

I will think about rules for Hl combined signals which are more diffcult in the following days.

This branch (Nakaner:hl-singal-integration) was forked from branch Nakaner:hp-light-signals-integration at commit 940b081.