make a new environment to store external data
Load big matrices into flycircuit::.extdata environment

* loading them into the global environment is bad style
* and will either result in things being overwritten or
  in spurious name clashes (e.g. attaching a big.matrix called 'mat' will be 
  aborted in an object of that name exists in .GlobalEnv
retire flycircuit.localroot option
retire 2 more options, allow remainder to be overridden and add docs
Merge branch 'feature/options'

* feature/options:
  retire 2 more options, allow remainder to be overridden and add docs
  retire flycircuit.localroot option
Merge branch 'feature/extdata-env'

* feature/extdata-env:
  Load big matrices into flycircuit::.extdata environment
  make a new environment to store external data
Add option for default score matrix
fix bug in setting of flycircuit.datadir option
set default score matrix to kcs20scores bundled with flycircuit package
Merge branch 'feature/default-scoremat'

* feature/default-scoremat:
  set default score matrix to kcs20scores bundled with flycircuit package
  fix bug in setting of flycircuit.datadir option
  Add option for default score matrix
remove remoteloc test and add scoremat one
fix broken help crossref
fix broken test for option state
fix missing import from ff
fix a couple of visibility issues now that score matrices go into .extdata
expect to be given url to .ff not .ffrds file
Correctly plot most and least similar KCs
set persistent default for plotting orientation (frontal to fly brain)
reuse rgl window
typo