Allow searching by Dates Issue: #7

Instead of storing date fields in the SearchAPI document, we store the date's time as Number field. This way we can execute queries by passing date with provided time (hour,minute,seconds) are retrieve more precise search results. A limitation is the max value that double can hold !

Local variable renaming

Search results now can be sorted by given sort field in ascending / descending order

Set default value for sorting to empty string.

Minor renaming and added test