Add support for backrefs in file names

[dirkrob78]

At my work I'm working with a lot of custom EDA tools that have redundant filename patterns. So, backrefs in the file names would useful, at least for me! Please let me know what you think. I did a few manual tests to check for navigating and completion working on both Windows and Linux.

For paths with redundancy, capture the repeating part of the path. Any * or ** in the pattern creates a capture group, which can be repeated with {1}, {2}, {3}, etc. Also, adds support for multiple single * groups, and for * before **. Can support up to one **, and it groups all extra matches into it like "x/y/z".

Example .projections.json:

{
    "src/config/*/{1}.cfg": {
        "type": "config",
        "template": "# Configuration for {}\n# Add your config settings here\n"
    },
    "*/{1}/**/*/{3}.abc": {
        "type": "abc",
        "template": "# Abc for {}"
    },
    "**/*/{2}/*/{3}.bcd": {
        "type": "bcd",
        "template": "# Bcd for {}"
    }
}

Examples:
:Econfig tmp -> src/config/tmp/tmp.cfg
:Eabc a/c -> a/a/c/c.abc
:Eabc a/x/y/z/c -> a/a/x/y/z/c/c.abc