Document how to use devstore2 & create public bag symlinks

The additional Make target creates symbolic links between the
directories representing system spaces and their public bag names that
devstore2 will use to find tiddlers belonging to the spaces.

There is also some notes for developers on how to install and use
devstore2 for local development.
Link app files with common space & clean correct common dir

The app files are part of tiddlyspace and should be symlinked.  The
files in the lib directory are copied over from an external source.

If these file are to be picked up automatically by devstore2 then the
developer should create the symlinks needed from the desired
repository to the src/common directory.
Remove mention to twimport in config - not needed.
Rename system space folders to match their public bag names
Merge pull request #1044 from pads/DevTweaks

Notes and some light assistance with local system tiddler development