Moved all adjacency matrix stuff to a separate module

src/.gitignore

@@ -3,6 +3,7 @@
 # Only track modules that are part of the plumed core
 !/Makefile
 !/README
+!/adjmat
 !/analysis
 !/bias
 !/blas

src/adjmat/.gitignore

+/*
+# in this directory, only accept source, Makefile and README
+!/.gitignore
+!/*.c
+!/*.cpp
+!/*.h
+!/Makefile
+!/README
+!/module.type