Subconvert

* ADD: getting FPS from avi files using MPlayer
* ADD: option to backup files if they exist (overwriting input files are back
them up automatically while output files are backed up explicitly)
* FIX: code refactoring. Until now subconvert reads whole files to the memory
which speeds it up almost twice
* FIX: bug where parsing empty files returned results

* ADD: force option
* ADD: verbose option
* FIX: writing a newly created file
* FIX: unescaped curly braces in microdvd and subrip that caused crashes

* ADD: SubRip and MicroDVD parsers/handlers
* ADD: Writing output to a file
* ADD: Automatic handling all newly implemented file formats