add wrapper functions for all database layer functions used in the drupal table storage handlers -- this paves the way for external databases via drupal's external database access.

add helper function from determining metric data type, use for both sampler init and ensure scheme metric function.

use select to discover existing metrics instead of db_affected_rows, as updates might not change anything.

initial crack at batch processing support for samples that have a large amount of objects -- untested.

911912 by hunmonk: views integration not reporting schema properly.  reworked sampler_build_drupal_metric_schema() so that it could be leveraged to fix this issue.

clean up confusing comments_per_node metric example, and set it to use the random method by default.

#914808 by hunmonk: move PHPDoc to interface definition only.  also added some missing methods to the interface, and removed saveSamples() by moving it entirely to the SamplerMetric() class.

adding a few more color options to example graph, and an error message when a sampler can't be loaded.

object_base_table and object_primary_key moved out of default_options attribute to root of metric properties array.