Allow .trace as input + some other enhancements

1. Allow to use raw fprof .profile file as input. It will be converted to .analysis automatically.
```
$ erlgrind fprof.trace fprof.cgrind  # will generate fprof.profile and then fprof.cgrind
```
2. Allow to pass only input file. Output file name will be generated from input by replacing extension with ".cgrind"
```
$ erlgrind my_fprof.profile  # will generate my_fprof.cgrind
```