webapi.rst: small edits to the t=relink section
ServerMap.copy(): deepcopy .update_data too. Closes #1785.

This was apparently unused, but good to copy for completeness. Tests
pass with and without the change.
attempt to clarify move-vs-relink
convergence secret doc by CtB, marlowe, zooko
s/node/client; mention restart is needed
bin/tahoe: clean up global-vs-subcommand arguments like --node-directory

The new rules for "bin/tahoe ARG1.. SUBCOMMAND ARG2.." arg:

* --node-directory is only accepted in ARG1, not ARG2
* create-*/start/stop/restart accept --basedir in ARG2, or an explicit
  basedir argument
* only one of --node-directory/--basedir/explicit-basedir is accepted
* --quiet/--version is only accepted in ARG1, not ARG2

Closes #166
rename VDriveOptions to FilesystemOptions
CLI: put "[global-opts]" in all command synopses
Remove the whitespace reported by find-trailing-spaces. No code changes.
test_cli: probably remove the unix-ism that broke tests on windows
docs: replace emdash characters with plain ASCII
Merge remote-tracking branch 'origin/master'