New update script & Documentation cleanup

[Nao-ris]

Updating to a new version of Couchbase Lite C is still done by hand, which is time consuming and error prone.
There was a script download.sh that could be used to download the different releases locally, but many manual actions were still required afterwards.

This PR introduces a new script, update_cblite_c.sh, that can:

1. Download all the needed releases from Couchbase Lite C in a temporary directory
2. Unzip all the packages in a temporary directory
3. Recreate the libcblite folder in a temporary directory
4. Replace the libcblite folder in the local repository with the one created
5. Strip the libraries

This should greatly help the release of new Couchbase Lite C versions.