Added frequency table to input
- resolved #7
- this is an example of an input file:

3
1 0 10 FIXED 1
2 0 11 MIN_MAX_UNIFORM 1 2 0
3 0 12 FREQUENCY_TABLE 3 1 10 2 50 3 40
10000

The first and the last line are the same as before.
Tasks share the same structure (id, phase, period, [fixed or random execution time]).
Three possible random execution times:
- FIXED - just follow up with an integer
- MIN_MAX_UNIFORM - follow up with three integers: min and max of the interval and distribution (not used)
- FREQUENCY_TABLE - N EXE_TIME_1 P_1 EXE_TIME_2 P_2 ... EXE_TIME_N P_N

TODO - use XML for frequency table