Edit make banksim to allow external injection file

[divyajyoti09]

Standard information about the request

This is a: new feature

This change affects: pycbc_make_banksim function

This change changes: documentation, banksim generator

Motivation

At the moment, only lalapps_inspinj function is allowed for creating injection file through the workflow generator pycbc_make_banksim. With this update, an externally created injection file can also be called.

Contents

The code allows for option to use inj.xml provided by user if the user chooses [external_injection] section instead of [inspinj] in the config file.

It also indicates the same in the documentation text.

Testing performed

I have tested it by generating the workflow using inj.xml generated by pycbc_create_injections. It works fine.

• [ x ] The author of this pull request confirms they will adhere to the code of conduct

[ahnitz]

You should probably shutil instead of a system command, otherwise this seems fine.