Support for CRON expression for backups and minor bug fixes

[A]: Fix for filtering by ColumnFamily name as ColumnFamily directory naming change was introduced in Cassandra 2.1.x.
[B]: Added CommitLog archiving properties file path config option
[C]: Support for CRON expression for backup was required so priam backup can be scheduled in more than one way (currently, it only supports daily backups). Need for taking more frequent or less frequent backups will be supported via CRON. This is done via adding following two configurations:

1. priam.backup.schedule.type and overriding the default value of TIME to CRON. Note that default value of TIME (for backward compatibility) makes the backup to look at the configuration for priam.backup.hour and behave accordingly.
2. priam.backup.cron. This configuration expects a valid CRON expression to be set for it to take effect. The impact of different values:
   i) -1: Disable backups. Similar to "priam.backup.hour" with a value of less than zero.
   ii) Invalid cron expression: Priam won't start and fail-fast. This is to ensure we are not starting priam with values which are not correct.
   iii) Default value: Take backup daily at 12.

For information on how to set up CRON timer refer to following documents -

• @link http://www.quartz-scheduler.org/documentation/quartz-2.x/tutorials/crontrigger.html
• @link http://www.cronmaker.com To build new cron timer