gstlal_svd_bank, cbc_template_fir.py, and svd_bank.py: Add an option to...

gstlal_svd_bank, cbc_template_fir.py, and svd_bank.py: Add an option to gstlal_svd_bank to indicate that whether we are creating banks of filters for producing signal candidates or for producing noise candidate. This information is recorded in the svd bank file so that the trigger generator knows the type of the triggers.