Touchy: Disable macro button if there aren't any macros defined

Previously, poking the macro button would generate a traceback if there are no
macros.
stepconf: Try to work better with duplicate IDs

This makes it safe to build one screen from multiple
unfortunately, we still can't detect until runtime that a duplicated
name is referred to from the Python code.

Signed-off-by: Jeff Epler <jepler@unpythonic.net>
Remove mistaken file
Let the splash screen run with default varfile

On a first startup, there are no G54 offsets, so the splash screen
will not run without touch-off.  This is confusing for new folks.

Having +Z allowed is the least bad solution for this I think,
because people do actually mill the splash screen into things,
so it should continue to have top of workpiece as zero.

Shipping and installing a nondefault varfile is the only other
solution I can think of, and that's nasty.
comment the funny Z max in sim/axis/axis.ini
update changelog and VERSION for 2.6.1