"Modify" for non-string values

Added the possibility to modify float, integer e bool values (using explicitly true/false)
Changing to some more meaningful names
Print number of tracks on disc to simplify the decision of switching to singleton mode
version bump: 1.1.1
Merge pull request #267 from jayme-github/album_itemcount

Print number of tracks when importing
rewrap and changelog note for #267
Merge pull request #265 from duailibe/modify

"Modify" for non-string values
move type conversion to commands module (#265)

This change also uses the existing str2bool utility function.
changelog/thanks for #265
Preliminary support for "date added" fields

This isn't yet finished, it needs some input on how to organize the data, and actually where to implement the use of this data, but it already works in setting the date
Using time.time() to store the import time
Formatting the import time in the view and paths

Added the %format{} template function to output the time to any format supported by time.strftime()