update URL with filename via pushState
consolidate filename subscribe with other call
Revert "consolidate filename subscribe with other call"

This reverts commit f43d0201995c4ddbdbdcaf855f64933237f095d0.
on page load, load worksheet by filename specified in URL anchor
attempt to highlight last segment, even when file loaded
fixed last (empty) segment to be highlighted as active on URL-based file load
after loading file manually, store filename in URL
show error and don't save, when attempt to create file that already exists
use 204 status for successful create/update
Merge pull request #3 from modellurgist/show-filename-as-url-anchor

Show filename as url anchor
Merge pull request #4 from modellurgist/prohibit-creating-files-with-same-name

Prohibit creating files with same name
set initial namespace to sessionID, to support multiple users
use Diceware's short word dictionary to generate a two-word namespace, instead of using long uuid