New icons for next openHAB Release

I have createt some new Icons to use in openHAB

* Inverter / solar inverter
![inverter](https://cloud.githubusercontent.com/assets/9118135/4581340/4be973ba-4fdf-11e4-9358-4213c9b684c1.png)
![inverter-off](https://cloud.githubusercontent.com/assets/9118135/4581338/4be544c0-4fdf-11e4-954c-856f8dd45030.png)
![inverter-on](https://cloud.githubusercontent.com/assets/9118135/4581339/4be94336-4fdf-11e4-980d-f442b47c0fda.png)

* Insert Heater or Smart Heater
![smartheater](https://cloud.githubusercontent.com/assets/9118135/4581341/4beb9e06-4fdf-11e4-835e-eb008ac1a31c.png)
![smartheaterhigh-off](https://cloud.githubusercontent.com/assets/9118135/4581346/4c08fbea-4fdf-11e4-9100-fd905d4fd017.png)
![smartheaterhigh-on](https://cloud.githubusercontent.com/assets/9118135/4581348/4c188146-4fdf-11e4-8f5a-17f8156308d8.png)
![smartheaterlow-off](https://cloud.githubusercontent.com/assets/9118135/4581342/4bff464a-4fdf-11e4-988b-df603bed2783.png)
![smartheaterlow-on](https://cloud.githubusercontent.com/assets/9118135/4581343/4c00a652-4fdf-11e4-931d-654d0905162b.png)
![smartheatermedium-off](https://cloud.githubusercontent.com/assets/9118135/4581344/4c04f1ee-4fdf-11e4-9225-f1233e9c8964.png)
![smartheatermedium-on](https://cloud.githubusercontent.com/assets/9118135/4581345/4c06ae30-4fdf-11e4-8c11-64027e37b2f4.png)
![smartheater-off](https://cloud.githubusercontent.com/assets/9118135/4581351/4c1dbbfc-4fdf-11e4-92c4-f281a82e8410.png)
![smartheater-on](https://cloud.githubusercontent.com/assets/9118135/4581347/4c164840-4fdf-11e4-83c7-6f0e1c2f85db.png)

* softener (Weichwasseranlage)
![softener](https://cloud.githubusercontent.com/assets/9118135/4581350/4c1c934e-4fdf-11e4-8906-7c0e695fc692.png)

* solar plant (house)
![solarplant](https://cloud.githubusercontent.com/assets/9118135/4581349/4c1a7122-4fdf-11e4-81ea-7612a4f5b286.png)