T2345: Replace instances of NULL with nullptr

The following changes have been applied to src and lib folders:
regex replace: ([^"_])NULL ⇒ \1nullptr (8968 chgs in src, 1153 in lib)
Manually find/change: (void \*) nullptr ⇒ nullptr (1 case)
regex find: ".*?nullptr.*?"
  Manually ~14 cases back to "NULL" in src, ~2 in lib
  regex finds a few false positive where nullptr appears between two
  strings in a function call

lib/atc/FundamentalAtomicQuantity.cpp

@@ -126,7 +126,7 @@ namespace ATC {
                                              double unitsConversion,
                                              AtomType atomType) :
     ShallowAtomQuantity<double>(atc,0,atomType),
-    computePointer_(NULL),
+    computePointer_(nullptr),
     computeTag_(tag),
     unitsConversion_(unitsConversion)
   {