fuzzy file searching within project
handle directories
use FileScanner; add some utilities
directly return whether results cacheable
remove some R functions from internal blacklist
use explicit
ensure 'cacheable' is a scalar
more work on caching, styling
create subsequence matching regex; re-work subsequence filter
'isSubsequence' regex generators; path offsetting
make more utilities available to R
make isSubsequence available to R; use it
remove completion list truncation for now

The truncation needs to occur elsewhere -- completions are ordered in
such a way that the most relevant 'type' of completions come first, e.g.
function argument completions should always be displayed first when
within an argument list.
add folder icon for directories
revamp file search to use project index  (recursively) when possible
index .r, .s, .q files
use a tree, rather than a set, to store file index
root node as empty label, since we don't include trailing slashes
further limit number of executions
allow more results to be sent to client