Bug 1096278 - Improve database plugin design to support connection
pooling

This changeset introduces a new API for database plugins and deprecates the previous one. Compatibility with the previous API will be maintained until next major version of RHQ.

The 'rhq-database-plugin' was based on org.rhq.plugins.database.DatabaseComponent interface which encouraged plugin authors to share a single JDBC connection across database components. This was wrong for various reasons (connection leaks, concurrent JDBC calls... etc).

The new API introduces three important classes:
* org.rhq.plugins.database.PooledConnectionProvider
* org.rhq.plugins.database.BasePooledConnectionProvider
* org.rhq.plugins.database.ConnectionPoolingSupport

BasePooledConnectionProvider is a base implementation of a PooledConnectionProvider. Plugin authors should create a concrete implementation of BasePooledConnectionProvider which overrides the #getDriverClass() method. This is important if a database plugin embeds a JDBC driver: the database-specific driver class must be loaded by the child plugin classloader.

ConnectionPoolingSupport helps to manage the compatibility with the old API. It's a contract that all new database resource components should obey to. It declares the following methods:
* #supportsConnectionPooling()
* #getPooledConnectionProvider()
Results of calls to #supportsConnectionPooling() #getPooledConnectionProvider() must be consistent. In practice, a top level server database component should be able to create a PooledConnectionProvider instance, and child servers and services should indicate they support connection pooling only if their parent component does.

The 'rhq-database-plugin' embeds the BoneCP library (JDBC connection pooling) and its dependencies (Google's Guava). Child plugins will have all the classes accessible as soon as they have this node in their plugin descriptor:
===
<depends plugin="Database" useClasses="true"/>
===

This changeset includes the necessary changes to support connection pooling in the Oracle, Postgres and MySQL plugins.

Thanks to Elias Ross for contributing the original patch from which this changeset is derived.

(cherry picked from commit 2b810f1c9fa247a9d8ddf08d2b9ba93c9e1cf2a6)

Conflicts:
	modules/plugins/mysql/src/main/java/org/rhq/plugins/mysql/MySqlConnectionManager.java
Bug 1096278 - Improve database plugin design to support connection
pooling

This changeset introduces a new API for database plugins and deprecates the previous one. Compatibility with the previous API will be maintained until next major version of RHQ.

The 'rhq-database-plugin' was based on org.rhq.plugins.database.DatabaseComponent interface which encouraged plugin authors to share a single JDBC connection across database components. This was wrong for various reasons (connection leaks, concurrent JDBC calls... etc).

The new API introduces three important classes:
* org.rhq.plugins.database.PooledConnectionProvider
* org.rhq.plugins.database.BasePooledConnectionProvider
* org.rhq.plugins.database.ConnectionPoolingSupport

BasePooledConnectionProvider is a base implementation of a PooledConnectionProvider. Plugin authors should create a concrete implementation of BasePooledConnectionProvider which overrides the #getDriverClass() method. This is important if a database plugin embeds a JDBC driver: the database-specific driver class must be loaded by the child plugin classloader.

ConnectionPoolingSupport helps to manage the compatibility with the old API. It's a contract that all new database resource components should obey to. It declares the following methods:
* #supportsConnectionPooling()
* #getPooledConnectionProvider()
Results of calls to #supportsConnectionPooling() #getPooledConnectionProvider() must be consistent. In practice, a top level server database component should be able to create a PooledConnectionProvider instance, and child servers and services should indicate they support connection pooling only if their parent component does.

The 'rhq-database-plugin' embeds the BoneCP library (JDBC connection pooling) and its dependencies (Google's Guava). Child plugins will have all the classes accessible as soon as they have this node in their plugin descriptor:
===
<depends plugin="Database" useClasses="true"/>
===

This changeset includes the necessary changes to support connection pooling in the Oracle, Postgres and MySQL plugins.

Thanks to Elias Ross for contributing the original patch from which this changeset is derived.

(cherry picked from commit 1eb8c728c0c1939115fe90bd1c91fbf5ecf0a036)

Conflicts:
	modules/plugins/mysql/src/main/java/org/rhq/plugins/mysql/MySqlConnectionManager.java