Allow disabling modules and extensions from module.properties

Discovery of modules is based on classpath scanning.  In some situations it
may not be possible or desirable to change the classpath.  To force a
module to not load you can create a file called modules.properties on the
classpath that can exclude specific modules from loading.  Additionally
this same file can be used to exclude a specific extension.  Extension
loading is typically done through global configuration.  If you want to set
up an environment and you don't even want the extension/module loaded on
the first start, then using the config file is appropriate.

Example: modules.properties

modules.exclude=storage-image-s3,storage-volume-solidfire
extensions.exclude=ClusterScopeStoragePoolAllocator,ZoneWideStoragePoolAllocator

Typically you would want to place this file in /etc/cloudstack/management
CLOUDSTACK-4736: Monitoring services in VR
Fixed some html validation errors

language tag in script is deprecated. used type
<script> tag after </html> is invalid. moved the localized messages dictionary inside html body.