Updates required to compile for KSP 1.8.x

• updated Framework to 4.5 and references to KSP1.8
• minor compile fixes
• fix startup error log:

get_dataPath is not allowed to be called from a MonoBehaviour constructor (or instance field initializer), call it in Awake or Start instead.
See "Script Serialization" page in the Unity Manual for further details.

NB: Not expecting this pull-request to be accepted as-is there is no 1.8 branch yet (what happened to using master?!); just putting this here FYI.