add a file for metric trees

to be used with the proof of the universal property for the circle
improve makefile

so it gets the filenames from each package, from the file
.package/files
remove all LoadPath commands
metric trees...
metric trees ...
metric trees ...
metric trees...
metric trees ...
metric trees ...
Merge branch 'master' of github.com:UnivalentMathematics/Foundations
metric trees ...
metric trees ...
new file Nat.v; add coq as submodule
nat as metric tree...
Merge remote-tracking branch 'upstream/master'
improve makefile, add CC0 notice to Ktheory package
fix makefile
fix Makefile
document installation in README
metric tree on nat, done