Added tower points and model layers and TOC.

Existing are green and proposed are blue.

Existing always draws on top of proposed.

Higher powers are always drawn on top of lower speeds independent of whether they are from existing or proposed towers. To achieve this I had to put all model data into a single dataset and use symbol levels. This prevents lower speeds from existing towers from hiding higher speeds from proposed towers.

I tried drawing the model data as a feature layer but it was unusable because of performance. So no transparency showing overlapping areas.

Tower points are loaded as a feature layers.

Closes #1