documentation fixes

src/analysis/Histogram.cpp

@@ -33,7 +33,9 @@ namespace analysis{
 //+PLUMEDOC ANALYSIS HISTOGRAM
 /* 
 Calculate the probability density as a function of a few CVs either using kernel density estimation, or a discrete
-histogram estimation. In case a kernel density estimation is used the probability density is estimated as a
+histogram estimation. 
+
+In case a kernel density estimation is used the probability density is estimated as a
 continuos function on the grid with a BANDWIDTH defined by the user. In this case the normalisation is such that
 the INTEGRAL over the grid is 1. In case a discrete density estimation is used the probabilty density is estimated
 as a discrete function on the grid. In this case the normalisation is such that the SUM of over the grid is 1.

src/bias/LWalls.cpp

@@ -31,7 +31,7 @@ namespace bias{
 
 //+PLUMEDOC BIAS LOWER_WALLS
 /*
-The LOWER_WALLS and UPPER_WALLS keywords define a wall for the value of one or more collective variables,
+Defines a wall for the value of one or more collective variables,
  which limits the region of the phase space accessible during the simulation. 
 
 The restraining potential starts acting on the system when the value of the CV is greater 

src/bias/UWalls.cpp

@@ -31,7 +31,7 @@ namespace bias{
 
 //+PLUMEDOC BIAS UPPER_WALLS
 /*
-The LOWER_WALLS and UPPER_WALLS keywords define a wall for the value of one or more collective variables,
+Defines a wall for the value of one or more collective variables,
  which limits the region of the phase space accessible during the simulation. 
 
 The restraining potential starts acting on the system when the value of the CV is greater