Add loadOnStartup attribute for the specifications

This commit includes also the use of java 7 synatx for generics and the
introduction of the CredentialManager
Implement the strategy of the HighestVersionSelector.
Create describing binding types in manifest package
Annotate member variables and fix related problems
Add a method to get a File object of the addons directory and addons conf directory
Implement AddonProperties and use them

This commits makes the Context constructor shorter.
Move addon.xml extraction in a separate class
Fill the FileRegistry on start and load everything with a loadOnStartup = true
Add new interface method listInstalledAddons() and add java doc

Furthermore the commit implements the new interface method in the existing AddonRegistry
implementations.
Add the AddonManager to the Constructor of the file registry.

Splits also the loadLoadOnStartAddons into two methods to load all addons and to load a single addon.
This is required for the case a new addon was added and the description contains a LoadOnStartup in
the manifest. In this case the manager have to invoke the init() function of the specific action.
Merge remote-tracking branch 'hm/addonManifest' into stage