create getInput function in input module
create getInput function in input module

allows to retrieve data from the input file by querying the global
rmg variable, or by searching for broadcasted variables.

Currently, only the "speciesConstraints" can be retrieved.

pierrelb/RMG-Py,nickvandewiele/RMG-Py,nickvandewiele/RMG-Py,chatelak/RMG-Py,pierrelb/RMG-Py,chatelak/RMG-Py,nyee/RMG-Py,nyee/RMG-Py