Refactorizations, fixes #44, #35, #34, #25

Refactorization of keyboard shortcuts: all shortcuts are now in separate class.
Refactorization of parsers: adding a new task/contest parser should be neater now.
Refactorization of execution results: chenged execution results to Enum. Adding new execution result requires less code now.
#25: All windows appear in the center of previous window.
#34: Right click on the problem tab and the option "delete" will appear.
#35: There are two abort buttons now: abort current test and abort all tests. Both work fine.
#44: Copy input button added. With shortcut ctrl+shift+c.
Other changes:
- Time limit is now editable. And task parser for Codeforces extract and set time limit for all tests.
- alt+[1-9] switches between problems.
- Added tool tip to parsing result label. Moving cursor over "parsing failed" shows message with exact parsing error.