enable features to be kept on database

[jreps]

The current function FeatureExtraction::getDbCovariateData forces the download of the covariates. The default covariate function FeatureExtraction:::getDbDefaultCovariateData has inputs such as targetCovariateTable that let the user skip the download of the covariates and instead inserts them into the specified database tables.

The cohorts as features covariate function does not let you specify a database and table to save results to.

It would be nice if all the covariates get functions such as FeatureExtraction:::getDbCohortBasedCovariatesData had these inputs:

• targetDatabaseSchema
• targetCovariateTable
• targetCovariateRefTable
• targetAnalysisRefTable

and when specified inserted the results to a database table rather than downloaded. Then there could be a new function such as FeatureExtraction::insertDbCovariateData that takes the same inputs as FeatureExtraction::getDbCovariateData but also has:

• targetDatabaseSchema
• targetCovariateTable
• targetCovariateRefTable
• targetAnalysisRefTable
  and instead of downloading the covariates inserts them all into the specified database and set of tables.

This would help any code that does further manipulation of the features as that can be done in SQL rather than R.

[anthonysena]

Linking this to #152 since it already has an implementation done some time ago by @azimov that I'll need to discuss with @ginberg.