Feature/upgrade db load

Upgraded DB Loadprocess
An error was discovered when loading the entire series xml file. The initial processing of series xml from theTvDb was too large to process in memory. SAX was used to streams the data instead of loading the entire xml into memory.  A custom handler that only looks for seriesid was created to pair down the data that needed to be stored in memory.

Added a method for filtering the data but is no longer needed at this point.  The method is bank but present if need in the future. Adult content was going to be filtered from the filter method but TV series only have a rating of TV-MA. Some of the popular show like "Game of Thrones" is rated TV-MA so this was not implemented.

Added constraint of nullable false for banner, fanart and poster in series. If any are missing we get a validation error and do not save. The series must not be popular if any of the three images are not present and the series is not load so that we conserve space. 

Added better messaging and exception handling to the TheTvDbApiService.loadASeries

Added store images of banner, fanart and poster

Added firstAirDate to episode domain

Added episodeNameLowerCase to episode domain

Added seriesNameLowerCase to series domain

Added a gsp to show an example of how to extract images from the database
This method allow user to pull any image from the database
```<g:createLink action='displayImageFromDatabase' id='${item}' params='[imageType:"banner"]'/>" ```