sgcollect should collect the installed version

Problem
Currently sgcollect gets the version via two ways:

1. Hitting an endpoint
2. Print the version in the header of the logs

Point one does not work when SWG is not running. Two can be pretty confusing as multiple versions can be printed out and then the timestamps have to be compared.

This makes the support tool much more complex.

Suggestion
The output of --version is captured and put into the sync_gateway.log

This will also be useful when checking to see if the running and installed versions match.

Workaround

In the mean time the following workaround can be used to find the installed version.

strings sync_gateway | rg /home/couchbase/jenkins | cut -d / -f 7 | uniq