Consider hoisting common target settings to the project level

[dempseyatgithub]

At the moment BSE performs all of its consolidation on the same 'level'. Common settings across multiple build settings at the project or target level are consolidated into a shared setting.

If there are common settings across multiple targets, they do not get hoisted to the project level.

For a more complex project, that may be desirable.

[dempseyatgithub]

Related to #27.