Add function to scan through neurons in 3D (dpscan)

Not sure if importing yaml package is the best way to go.
Merge pull request #24 from ajdm/dpscan

Add function to scan through neurons in 3D (dpscan)
Add return for downloaded file in fc_download_data()
Add as.data.frame.APResult()
Change fc_nblast() to use normalisation like sub_score_mat()
Merge branch 'ajdm-master'

* ajdm-master:
  Change fc_nblast() to use normalisation like sub_score_mat()
  Add as.data.frame.APResult()
  Add return for downloaded file in fc_download_data()

Conflicts:
	NAMESPACE (2 methods added at same line; re-ran roxygen to fix)
Add function to load SI data
Add documentation for load_si_data()
Remove underscores from option name
Update load_si_data() to handle other kinds of file and also return path