fix bool value conversion for version 1.4

[JuliaSprenger]

'False' as well as 'F' are not properly converted to bool value in formatConv branch

p = odml.Property(name='myprop', value=['False','F'],dtype=odml.DType.boolean)
print(p.value)
# -> [True,True]

[mpsonntag]

Just fyi: This issue is Python2 only, Python3 works as intended.