Better wording in the verified command help texts

Change-Id: I74b4a061bb8ae01600a8f74c5d12a2afcbc58329
Replace deprecated `gerrit approve` with `gerrit review`

The `approve` command is deprecated since Gerrit version 2.1.3.

Replace it with `review` throughout the code.

Change-Id: Iada958c16f630fb171459bc38214984e398c65a6
Fix indentation in help files

Indent with spaces rather than tabs.  Use correct indentation levels.

Change-Id: If97d4a2255e757cdbf9e72c8894e872fb99e6ab3
Rename constants for better readability and consistency

The constants `PROTO` and `GERRIT_PROTO` are renamed to `SCHEME` and
`GERRIT_SCHEME`.  This makes the naming of all the provider constants
consistent with RFC3986 [1].

The `proto` field is replaced with `scheme`.  The methods to get and
set `proto` are deprecated and new methods to get/set `scheme` are
added.

JSON parsing is modified to use `proto` if it exists, or otherwise
use `scheme`.

[1] http://tools.ietf.org/html/rfc3986

Change-Id: I38890355daa5d614e6b43fd351b199ed4f9e83c1
Fix grammar in help descriptions of Gerrit provider fields

Change-Id: I7a44a842e32a6bcccc81b829abd6d1b1a7afeedb
Add missing event types in description of change events

Change-Id: Ie066e281c7c20a432616c0668d076e18254df25d
Fix minor typos in comments

Change-Id: Ia8b00bd0f8b6f981b6c35f9f1f28089f1ed2ec9a
Change.java: Put imports of static constants in alphabetical order

Change-Id: I0321279b1aeed954c536733c9b2c77427282fe30
Make the change's full commit message available in triggered jobs

The full commit message is made available as an environment variable
in triggered jobs in Jenkins:

    $GERRIT_CHANGE_COMMIT_MESSAGE

The environment variable is only set if the JSON data received from
Gerrit's `stream-events` command contains the `commitMessage` field.

The `commitMessage` field is available from Gerrit version 2.8.

Change-Id: I657d6c28c8ae05a8d1fc9c328f92677231c294cd
Merge branch 'i' of gerrit-trigger-plugin