Updated version number and added script for updating the extension from v1.0 to v1.1

Added the script to update the extension from version 1.0 to 1.1. Other than the script, also updated the version number in other places in the code.

Steps to update from 1.0 to 1.1:
(i) Download and install version 1.1
(ii) Restart the postgres server in order to load the new 'cstore_fdw.so' file.
(iii) Run the command "ALTER EXTENSION cstore_fdw UPDATE;"

To check if it worked properly, you can do a "select * from pg_available_extensions;" and check that the installed version for cstore_fdw is 1.1.