GenericParser now stores parsing results in internal list

To fetch the results, method get_results() has been added
Added new GUI initializing.
Created SubConverter class.

* Class replaces global functions gathered in Convert module;
* it should be able to parse a single file, modify parsing results (i.e. modify each single sub
  section independently) and return modified output. It should also be able to convert modified
  output to any specified subtitle format;
* currently only parsing file, converting to the new format and returning converted output is
  implemented.
Added some functions that modify parsed subtitles
Added displaying subtitle files
Display all subs info (number, time and text) in a table
Added FileUtils and GUI files (should be added earlier but I forgot it :/)
Added changing FPS to FrameTime interface
FrameTime work
Fixed FrameTime tests
Changed FrameTime declarations in Parsers
Implemented changing FPS to the converter.
SubConverter.parse() now requires a list from which it'll read parsing input
SubConverter is encoding independent.

File should be decoded to utf-8 and then encoded back to user-specified output encoding.