Added Filters activity layout xml
Modified all the necessary xml to make the image filtering activity work 

- added relative lines in the strings.xml
- added "Filters" in the gallety_option.xml menu
- added the filter activity in gallery.xml
- added the new activity in the manifest
Fixed a bug in the DB.java file 

- removed wrong "=" operators in the getPhotos(Calendar from, Calendar
to) query
Updated the GalleryAdapter to show up only the filter images if a filter
is selected
Updated the GalleryActivity to get and pass the filter values
Implemented the Filter activity

- it chooses between some filter to display only selected Photos in the
gallery
Merge remote-tracking branch 'origin/master'