Fixed plumed_cmd("getBias")

Two bugs where there:
1. It was only working with double precision MD codes
2. It was returning energy in PLUMED units and not in MD ones

Both are fixed now

CHANGES/v2.0.txt

@@ -113,6 +113,8 @@ For users:
 - Several small fixes in documentation and log file.
 
 For developers:
+- Fixed cmd("getBias") to retrieve bias. It was not working with
+  single precision codes and it was not converting units properly.
 - Fixed a regression in 2.0.2 concerning include files from installed plumed
   (see commit 562d5ea9dfc3).
 - Small fix in tools/Random.cpp that allows Random objects to be

src/core/PlumedMain.cpp

@@ -310,7 +310,8 @@ void PlumedMain::cmd(const std::string & word,void*val){
   } else if(word=="getBias"){
        CHECK_INIT(initialized,word);
        CHECK_NULL(val,word);
-       *(static_cast<double*>(val))=getBias(); 
+       double x=getBias()/(atoms.getMDUnits().getEnergy()/atoms.getUnits().getEnergy());
+       atoms.double2MD(x,val);
   } else {
 // multi word commands