Added --build and --drop to the cta-statistics-save so that we can create and drop the tables needed for the statistics

This reverts commit c3c29b9aae562c2cc945b9c0e260d090d49c0b2f.

Changed the Placeholder_String::get_string() method
Changed the MysqlStmt::bindString so that it instanciate a Mysql::Placeholder_String object with a buffer that will have the size of the parameter to bind (if provided)

This reverts commit 20c4f60a.

Xrootd errors reported as a WARNING if the run was otherwise successful. ERROR otherwise as these xrootd failures could be the reason of the run failure.

(for failed archive jobs only)

Added 'immediately after m_stmt.executeQuery()' log message to facilitate debugging of 'cta-admin tapefile ls'

Adapted the unit tests + the database-dependencies on this removed column

Removed diskInstance attiribute from the common::dataStructures::StorageClass class
Adapted unit tests
Adapted cta-admin commands

StorageClass now belongs to a VO (madatory)
Adapted unit tests
Modified cta-admin command to set the VO of a Storage Class

Deleted Schema version 1.2
Adapted tapepool management so that it works with the new VIRTUAL_ORGANIZATION table
Adapted unit tests so that a VO is created before a tapePool is created
Adapted prepare_test.sh so that it creates a VO before creating the TapePool

Added deletion of existing VOs in the SetUp() method of CatalogueTest