Enhance ability to overwrite spark properties values through plugin

The attached patch contains:

-improved Spark Resources management: SparkRes.java and Default.java
by adding a new SparkPropertyResourceBundle as a wrapper around resource bundles
instances from SparkRes or Default

When a property value is retrieved, first is looked in a specific plugin location.
If not found it falls back to the Spark default property value

You simply add spark.properties and default.properties with keys/values you want overwritten by plugin
inside plugin's .jar archive file

NOTE: this patch needs SPARK-1312 attached patch

Please review
Thanks

I am attaching a test plugin as an example how spark properties values can be overwritten
The class plugin has no functionality (java source included in jar)

I changed the application name into: My Spark

APPLICATION_NAME = My Spark
in default.properties inside testPlugin.jar

The attached patch does not scale very well when many plugins are installed, some of the properties are not correctly overwritten in this schenario.

I will post a new patch that better handles resource props overriding

New patch attached
Patch description:

-load plugin resources into dedicated HashMaps at plugin loading phase
-in spark look for plugin key/value pair in hashmaps first. If not found - fall back to spark key-value pair

commited an improved version of the patch
we now are offering full spark resource overwriting support through plugin:
spark.properties, default.properties, spark_118n.properties (including localization) and preferences.properties to overwrite preferences defaults

r12573 = 8b197eb26154943ea40c9e68346e55fb5d92a889

Description:

-improved Spark Resources management: SparkRes.java, Default.java, Res.java, LocalPreferences.java
by adding a new PluginRes.java that contains hash maps with plugin resource values for
spark.properties, default.properties, spark_i18n.properties (and localization support), preferences.properties
that you want to be overwritten in plugin
The plugin can overwrite few preferences as well in preferences.properties:
toasterPopup
notifyOnOffline
notifyOnOnline
showTypingNotification
useAdHocRoom

PluginManager calls loadPluginResources() to load all plugin resources using the plugin' class loader
and puts them in dedicated hashMaps.
When a property value is retrieved, first is looked in the PluginRes corresponding's hashMap.
If not found it falls back to the Spark default property value

You simply add spark.properties, default.properties, spark_i18n.properties (and language specific spark_i18n_xx.proeprties),
preferences.properties with keys/values you want overwritten by plugin inside plugin's .jar archive file

commited

r12593 = 5154538af5f9667b329f2d8db5a474bbcd77f3bc

-make Spark user personal directory configurable through plugin (create dedicated properties key/value pairs in default.properties)

Mass closing of resolved issues