At least 1 report directory should be mandatory for parse command

[dkrupp]

Do not accept 0 positional arguments for parse command as it can lead misleading behavior as it will not find reports as either CodeChecker analyze or CodeChekcer check has default output report directory.

So at least 1 positional arguments must be mandatory.

usage: CodeChecker parse [-h] [-t {plist}] [-e {html}] [-o OUTPUT_PATH] [-c]
                         [--suppress SUPPRESS] [--export-source-suppress]
                         [--print-steps]
                         [--verbose {info,debug,debug_analyzer}]
                         [file/folder [file/folder ...]]

Parse and pretty-print the summary and results from one or more 'codechecker-
analyze' result files.

positional arguments:
  file/folder           The analysis result files and/or folders containing
                        analysis results which should be parsed and printed.
                        (default: /home/ednikru/.codechecker/reports)

[whisperity]

This heavily contradicts the default behaviour of CodeChecker analyze which will use the folder under the "workspace" for output.

Why are we making it so hard for people who just want to use CodeChecker with default settings?