Feature: mod groups

[bicobus]

It would be useful to group mods when the list gets especially long, and have the ability to collapse the sub tree and reduce visual pollution.

Groups would be determined by the filename. Proposed format: GROUP= filename.ext. The GROUP= element would be stripped from being displayed and an empty entry with that name would be created instead.

Tree would look like:

├── GROUP
│   ├── filename.ext
│   └── filename2.ext
└── regular file.ext

Tasks:

• Figure out if list's items can have collapsing sub tree.
• Convert the list to a table if previous task is unfeasible.
• A group should be able to be mass installed, related to Feature: install all mods #35