Add new SSH command to search in Gerrit documentation index

$>ssh review gerrit apropos capabilities
Gerrit Code Review - /config/ REST API:
http://localhost:8080/Documentation/rest-api-config.html

Gerrit Code Review - /accounts/ REST API:
http://localhost:8080/Documentation/rest-api-accounts.html

Gerrit Code Review - Project Configuration File Format:
http://localhost:8080/Documentation/config-project-config.html

Gerrit Code Review - Access Controls:
http://localhost:8080/Documentation/access-control.html

Gerrit Code Review - Plugin Development:
http://localhost:8080/Documentation/dev-plugins.html

Gerrit Code Review - REST API:
http://localhost:8080/Documentation/rest-api.html

Gerrit Code Review - /access/ REST API:
http://localhost:8080/Documentation/rest-api-access.html

Change-Id: I26d067e8e6e5056a53d25457361b079e437f4fd0
12 files changed