Add "entities" flag to pack command.

[duosii]

Roughly implemented an "entities" flag to the pack command, which is a path to a csv file.

The entities CSV is structured as follows.

...
production/upload/00/00401ec42e20c5704dd17f0c612519bf65e586,2.1.0,353,zB1ZZ07z8vwNIPkI5A5CSqZIQ12XML_bm0gdcXsJRPU,common
production/upload/00/011e0ac39760c129b00ad5df0ca2b36def3fd2,2.1.0,47104,mrEFDAgtaLKQp8O5fvXgNVpKtRNum3tr_IgPM4kWzc8,common
production/upload/00/0163bf21e1a2c6f39b4dabeab0f71bd5949c87,2.1.108,3270,qfyRnDokWJgSDPHKGjzc8t6nLZu73GwU0rswE7vRXy0,common
production/upload/00/01f94925f962d9e02b3d7a455dab60ea4285f2,2.1.0,36864,kpl6xskPbN2aFOChpP9A_ewFQ7IQn57INR5jhpvohzc,common
...

If this flag is provided, the pack command will no longer only place its output inside of the upload folder.
Instead, it will parse the entities CSV to properly place each packed file into its correct folder, such as medium_upload.

This is a rough implementation, so feel free to change whatever.
For example, right now the output of parser.getSrc is almost entirely wasted in order to recalculate the proper path.