Allow specifiying relative paths in the --file option without *

[vodorok]

With this modification, the --file option would allow passing paths with folder prefixes.

Consider a compilation json that contains a . in the directory fields, with the following example directory layout:

.                            
├── compile_commnands.json
├── include                                
│   └── lib.h                    
├── lib                                                                               
│   └── lib.cpp                                                                       
├── Makefile                                                                          
└── src                                                                               
    ├── a.cpp            
    └── b.cpp  

Before this patch, you could only specify path to source files with the --file option, that were not absolute is to add a * before the directory name.
CodeChecker analyze ./compile_commnands.json -o ./reports --file "*src/b.cpp"

After this patch the following two methods will also work:
CodeChecker analyze ./compile_commnands.json -o ./reports --file "./src/b.cpp"
CodeChecker analyze ./compile_commnands.json -o ./reports --file "src/b.cpp"

TBD.:

• Documentation changes

[dkrupp]

Implemented by #4250