General pattern for manager classes

A manager class is one that's used to talk to a noun-based section of the Management API as documented at http://docs.marklogic.com/REST/management. Each section of the API should have a manager class, and some may have multiple manager classes because the noun represented by the section encompasses several lower-level nouns. For example, the Databases and Forests sections should each have a manager class, while the Security section would have manager classes for users, roles, amps, and the other nouns encompassed by "security".

Each manager class should be named after the singular form of the noun that it represents - e.g. DatabaseManager, ForestManager, HostManager.

Each manager class should be placed in a package under com.marklogic.appdeployer.mgmt that corresponds to the name of the section that it represents. For example, the Databases manager should be located at com.marklogic.appdeployer.mgmt.databases.DatabaseManager.