There is a new way to create a new grammar based on an existing grammar:
by extending it. (It is also possible to clone an existing grammar, a before.)
Instead of showing nothing, show disabled buttons and some expanatory text to
provide guidance for users getting started with example-based grammar writing.
+ Preparations to support more target languages. Tested with Swedish.
+ Don't enable example-based editing if there is less that two concrete
languages in the grammar.
+ Don't show the "By example" button until the required lincat has been defined.
+ Remember the chosen language for examples.
"gf -server" mode now contains everything needed to run the minibar and
the grammar editor (including example-based grammar writing).
The Setup.hs script installs the required files where gf -server can find them.
These files have been moved to a new directory: src/www.
The separate server program pgf-http is now obsolete.
