Config JSON: provide support for type declaration in C style.

Users can use the `--config` argument to specify extra info to RetDec in form of a path to the config file with such info. Right now users can provide a type of the objects only in LLVM IR syntax. As RetDec can be easily integrated with other tools we should add more options to provide type info, for example, C syntax which could come handy as some tools export data types in this syntax (radare2).

```json
{
"globals": [
{
"name": "globy",
"type": {
"llvmIr": "%str = type {i32, {i8, {i32}}, i16, i16}"
}
},
...
]
}
```

```json
{
"globals": [
{
"name": "globy",
"type": {
"C": "struct str { int a; struct { char b; struct { int c; }; }; short d; short e; };"
}
},
...
]
}
```