Fixed issue when resolving reference to declaration 'settings' and
renamed subtemplate

(belongs to issue #13)
Removed accidentally set annotation @Nonnull on primitive types

(belongs to issue #5)
Small changes on documentation
Renamed exception to be concise to our naming convention
Removed accidentally set annotation @Nonnull on primitive types

(belongs to issue #5)
Improved documentation on class-level
Updated Guava for testing purposes to version 15.0; Updated PITest to
version 0.31 and Wagon SSH to version 2.5