added option 'concatenation.inMemory'

#		- (drs) fixed bug in
'PotentialNaturalVegetation_CompositionShrubsC3C4_Paruelo1996': if no
vegetation was estimated for the components to be estimated and the
fixed ones summed up to 0, then the result contained NA: now,
vegetation is forced > 0
#		- (drs) fixed bug in section of concatenation: if actions included
concatenation and ensemble, but not aggregation, then no concatenation
occurred mistakenly
#		- (drs) added option 'concatenation.inMemory':
#concatenation.inMemory: all temp output is loaded into a giant
data.frame, then written to final file; if !concatenation.inMemory,
temp output is read and immediately appended to final file
#		- (drs) renamed function 'collect_ResultsWithTemporaryDataFrame' to
'concatenate_TemporaryResultFiles'
#		- (drs) added two functions 'concatenate_TemporaryResultFiles': one
to concatenate in memory (as before), one to concatenate via append
(new); these are selected via option 'concatenation.inMemory'