mergedrl: Merge KiCad drill files

Import from https://github.com/9dof/kicad-utils
panelize.py: Import from http://blog.borg.ch/?p=12
panelize.py: Rename to panelize.py
panelize.py: Use float instead of int for coordinates values

KiCad now use metric system and millimeter unit as default. Most parsed
values must be read and written as float to adapt to this change.
This commit reads and writes, in millimeter, as float:
 - Coord() arguments
 - charwidth
 - charheight
 - linewidth
This is not past-proof, as it should be better to read the file Units:
field and adapt the reading/writing accordingly.
panelize.py: Do not transform module names

Keep same module name on all boards, as those names are printed in
silkscreen.
If the name is transformed, it becomes, e.g.: U2_C1, which is longer
and disrupt silkscreen organisation and not compliant with schematic
names.
panelize.py: Add DRAWSEGMENT cloning

DRAWSEGMENT is used (among other things) to draw PCB edge cut, which is
nice to have in panelization, even though it needs to be edited after
panelization is done to keep only boards outer edges.
Update README