Split off api classes from giant server lib

Moves the following classes to break dependency cycles:

 * GpgApiAdapter
 * AccountExternalIdCreator
 * AccountInfoComparator

Change-Id: Ie081b5d95d7b79f888650752fd55cc4a80f7ef42

Documentation/dev-plugins.txt

diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index dada623..8774ed2 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -2249,7 +2249,7 @@
 link:rest-api-accounts.html#create-account[account creation] REST API and
 inject additional external identifiers for an account that represents a user
 in some external user store. For that, an implementation of the extension
-point `com.google.gerrit.server.api.accounts.AccountExternalIdCreator`
+point `com.google.gerrit.server.account.AccountExternalIdCreator`
 must be registered.
 
 [source,java]